Sharply bitter or pungent (5)
I believe the answer is:
acrid
I believe this clue is a double definition.
'sharply bitter' is the first definition.
(I've seen this in another clue)
'pungent' is the second definition.
(I know that pungent can be written as acrid)
(Other definitions for acrid that I've seen before include "Strong and sharp" , "Having a bitter taste or small, like smoke" , "Bitter or corrosive" , "Stinging" , "Sarcastic" .)