Sharp sting (5)
I believe the answer is:
smart
I believe this clue is a double definition.
'sharp' is the first definition.
(similar in meaning)
'sting' is the second definition.
(I know that sting is a kind of smart)
(Other definitions for smart that I've seen before include "well-kept" , "Clever, ingenious" , "Sting - witty" , "Trim - sting" , "Chic - hurt" .)