Cardio Vs. Strength Workout

I know there have most likely been around a million of these topics, but I am trying to get my strength and definition back. I do cardio about 3-4 times a week at 35-45 mins. and do some resistance training mixed in. I know I need to increase the resistance training, Im not trying to bulk up, mostly getting that toned/definition back. Im 33, 5'11 and about 155. I tend to put weight on easy so Im just looking for some workout routines/suggestions to do this and not put bad weight on. All input is much appreciated and sorry for the novel.