Clever as a card could be (5)
I believe the answer is:
smart
'clever' is the definition.
(similar in meaning)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for smart that I've seen before include "Bright or dapper" , "Clever; sting" , "Elegant and stylish" , "Clean, tidy; clever" , "Chic - hurt" .)