Young swimmer in a drunken revel (5)
I believe the answer is:
elver
'young swimmer' is the definition.
(I've seen this before)
'drunken revel' is the wordplay.
'drunken' indicates an anagram.
'revel' with letters rearranged gives 'ELVER'.
'in a' is the link.
(Other definitions for elver that I've seen before include "Little fish" , "A baby eel" , "Young, migrating eel" , "New slipper" , "Young migratory fish" .)