Imitating (3)
'imitating' is the definition.
('ape' can be a synonym of 'imitate')
This is the entire clue.
(Other definitions for aping that I've seen before include "Imitation" , "Making copy of" , "Mimicking like monkey" , "Taking off" , "Trying to repeat" .)
(Another definition for ala that I've seen is " side petal".)