At a social event maybe wearing a suit's best (8)
I believe the answer is:
outsmart
'best' is the definition.
(outsmarting is a kind of besting)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for outsmart that I've seen before include "Defeat by more skilful manoeuvring" , "Win by clever thinking" , "Best" , "Outwit" , "Fool" .)