Sailor came back before the swim (5)
I believe the answer is:
bathe
'swim' is the definition.
(bathe can mean to swim)
'sailor came back before the' is the wordplay.
'sailor' becomes 'ab' (abbreviation for able seaman).
'came back' says the letters should be written in reverse.
'before' is a charade indicator (letters next to each other).
'ab' reversed gives 'ba'.
'ba'+'the'='BATHE'
(Other definitions for bathe that I've seen before include "Suffuse" , "Swim for pleasure, and clean oneself" , "Swim or paddle" , "Wash by immersion" , "Go swimming" .)