Criticises taps (6)
I believe the answer is:
knocks
I believe this clue is a double definition.
'criticises' is the first definition.
(I've seen this in another clue)
'taps' is the second definition.
('knock' can be a synonym of 'tap')
(Other definitions for knocks that I've seen before include "Strikes with a sharp blow or finds fault with" , "Raps, taps" , "Bangs on door" , "Raps; criticises" , "Raps on the door" .)