To get lean, defined legs you should always incorporate some thigh exercise into your program. There are an extraordinary amount of movements you can do to work this muscle from a variety of angles so you should never be at a loss for what to do or let boredom prevent you from having a good workout.
Two of the biggest thigh exercise movements that should be included are the squat and the lunge. These would basically be considered 'king' because they utilize the most muscle fibres and are usually the movements where you can use the most weight. Since with strength training you want to be using your time most efficiently, these two movements are perfect.
After those two, a few other thigh exercises you can do are leg extensions, one legged squats, jump squats, split squats, leg press, turned out squats or box jumps. All of these will target in and help improve either strength or explosive power.
If your main goal is not to develop a lot of size on your legs than simply don't perform as many different variations and don't provide a calorie surplus with your diet. If you aren't eating enough to grow muscle tissue, there is no way any amount of weight training will make you grow bigger - in fact, if anything it may make you smaller. Still perform the same movements though, squats and lunges, as they will burn the most calories while performing them and actually help aid the weight loss process.
Remember to give yourself a long enough rest period between the activities as well so you can put forth one hundred percent of your strength and power. If you are only giving half your effort during your workouts you are not going to see results nearly as quickly which is why rest is so vital.