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