See a retrograde revel as smart (6)
I believe the answer is:
clever
'smart' is the definition.
(similar in meaning)
'see a retrograde revel' is the wordplay.
'see' becomes 'C' (the word for the letter, according to Chambers).
'a retrograde' shows that the letters should be reversed in order.
'revel' written backwards gives 'lever'.
'c'+'lever'='CLEVER'
'as' is the link.
(Other definitions for clever that I've seen before include "Brainy, smart" , "Quick, skilful" , "Deft, able, bright" , "brilliant" , "Highly intelligent" .)