Annoys agents searching for drugs, we hear (5)
I believe the answer is:
narks
'annoys' is the definition.
('nark' can be a synonym of 'annoy')
'agents searching for drugs we hear' is the wordplay.
'agents searching for drugs' becomes 'narcs' (narcotics officers).
'we hear' shows a homophone (sound like).
'narcs' sounds like 'NARKS'.
(Other definitions for narks that I've seen before include "singers" , "Annoys; informers (sl.)" , "Coppers' ..... are slang police informers" , "Irritates" .)