Mischievous chimp is hassling constituents (6)
I believe the answer is:
impish
'mischievous' is the definition.
(I know that mischievous can be written as impish)
'chimp is hassling constituents' is the wordplay.
'constituents' says the answer is hidden in the clue (I've seen 'constituent' mean this).
'IMPISH' is hidden in the letters of 'chimp is hassling'.
(Other definitions for impish that I've seen before include "Mischievous like small devil" , "Wicked" , "Teasingly mischievous" , "Naughty" , "troublesome" .)