Clever, astute (5)
I believe the answer is:
smart
I believe this clue is a double definition.
'clever' is the first definition.
(similar in meaning)
'astute' is the second definition.
(similar in meaning)
(Other definitions for smart that I've seen before include "Upmarket" , "Alick" , "Chic - hurt" , "Sharp stinging pain" , "Clean and stylish" .)