Taking off (4)
'taking off' is the definition.
(less can mean take away or subtracting)
This is all the clue.
(Other definitions for less that I've seen before include "Smaller in amout or degree" , "In smaller quantity" , "inferior" , "See 12" , "So-called St James" .)
(Other definitions for apery that I've seen before include "Imitative behaviour - repay (anag)" , "imitation" , "Take-off" , "Mimicry" .)