The first thing people do when they want to lose some fat is up the cardio, so If you are doing traditional aerobic activity to burn fat dropping that shit would be the first step. It elevates cortisol levels and is counter productive to muscle gains.
The next step would be to replace it with an ass kicking anaerobic workout that last between say 4 and 20 minutes. An example of this would be many of the crossfit style workouts, but you could string anything together or just do tabata style cyclic work, 20 seconds on, 10 seconds off for 8-10 rounds. It could be rope jumping, sprints etc but the key is to try and jack your heart rate during the 20 second work phase. Because its anaerobic work and short duration it wont be as detrimental to muscle mass as long duration low intensity cardio. It also generally burns more fat in a shorter period of time PLUS has shown to have a long term(ie 24 hours) systemic effect on your metabolism which causes ongoing lipolysis.