“Skinny” male swimming with pride (9)
I believe the answer is:
'skinny' is the definition.
'male swimming with pride' is the wordplay.
'swimming with' is an anagram indicator.
'male' with its letters anagrammed with 'pride' makes 'EPIDERMAL'.
(Other definitions for epidermal that I've seen before include "Relating to skin surface" , "Like protective covering" , "Of the outer skin" , "Like skin" .)