If you plan on doing this in quest mode,
When defeating dancers in the executive sector of quest mode you have to completely knock them out without letting time run out, if you do not knockout the dancer before time runs out, it will count as a win but you will not receive the hidden track for that specific dancer.
So to unlock this achievement you need:
16/16 CLUB CHALLENGES
4/16 EXECUTIVE DANCE BATTLES (DEFEAT OPPONENT BEFORE TIME RUNS OUT)
I unlocked the achievement for ''beat 20 clubs'' without unlocking ''20 hidden tracks''. I thought my game was glitched, I had to learn the hard way before unlocking ''20 hidden tracks'' later on.