We don't normally speak as though having a desire for something implies that we presently feel some inclination to acquire it. It makes sense to say that I have a desire for Thai curry even if I'm currently taking a driving test and not thinking about Thai curry at all. Therefore it's tempting to say that "having a desire" can be cashed out in terms of a fairly straight-forward counterfactual. I would have a desire for Thai curry just in case the following is true:
(1.) If I were sufficiently deprived of Thai curry and entertaining the possibility of acquiring it, I would feel in an inclination to acquire it.
I don't think (1) does justice to the nuances of desire-possession. Consider another account offered by Xunzi (Hsün Tzu, 3rd Century B.C.E.). On the one hand Xunzi holds that our natural desires are susceptible of being utterly transformed. On the other hand Xunzi also claims that certain inclinations are permanent, such as the eyes' lust for beautiful things. The eyes will always lust for such things when allowed to dwell on them, but it's also true the eyes' lust can be refashioned into a desire for sights that are consistent with virtue. How is this possible? Consider the following passage:
[The gentleman] makes his eyes not want to see what is not right, makes his ears not want to hear what is not right, [etc.]...He comes to the point where he loves [learning the Way], and his eyes love it more than the five colors, his ears love it more than the five tones, [etc.]...For this reason, power and profit cannot sway him. ("An Exhortation to Learning," Ivanhoe and Van Norden, pp. 260-61.)
A strong claim about the possibility of radical self-transformation, to be sure. But notice that Xunzi isn't suggesting that we can entirely eliminate the disposition to lust for beautiful things when allowed to dwell on them. Rather, the eyes develop a preemptory desire to avoid dwelling on the wrong things in the first place--a power of selective perception. With sufficient reinforcement it no longer makes sense to say that we have a desire for beautiful things as such, even though our eyes would lust for them if our thoughts were allowed to linger on them. This gives us a slightly more nuanced account of having a desire for beautiful things:
(2.) If I were sufficiently deprived of beautiful things and presented with an opportunity to entertain the thought of acquiring them, I would feel an inclination to acquire them.
Of course, I can be presented with an opportunity to entertain the thought of acquiring something without actually entertaining that thought. So on this account I could have a desire for beautiful things in sense (1) without having it in sense (2).
I think (2) sits closer to our usual way of understanding desire-possession. If I allowed myself to dwell on the thought of taking someone's fancy new laptop, I would probably feel an inclination to do so. But it's highly unusual for me to contemplate such a thing. I can sit in a classroom for hours without noticing open bags and backpacks that might have laptops inside. Often students will use their laptops in class and it won't even register. In contrast, a kleptomaniac would be well aware of those open bags, and would need to remind herself that it would be wrong to steal them.
So I have the desire in sense (1), because I would be tempted to acquire the laptop if I thought about it. But I don't have the desire in sense (2), because I don't in fact think about it (unlike the kleptomaniac). For purposes of evaluating moral character, (2) strikes me as the more decisive sense of having a desire.