Different parts of a swimmer (5)
I believe the answer is:
sprat
'a swimmer' is the definition.
(sprat is a kind of fish)
'different parts' is the wordplay.
'different' indicates anagramming the letters.
'parts' anagrammed gives 'SPRAT'.
'of' acts as a link.
(Other definitions for sprat that I've seen before include "little fish" , "It's set to catch a mackerel" , "Small edible fish" , "Small fish, sardine, say" , "Small marine fish" .)