Fine and well-built swimmer (5-4)
I believe the answer is:
hunky-dory
'fine' is the definition.
(I know that fine can be written as hunky-dory)
'well-built swimmer' is the wordplay.
'well-built' becomes 'hunky' (both can mean strong or muscular).
'swimmer' becomes 'dory' (dory is a kind of fish).
'hunky'+'dory'='HUNKY-DORY'
'and' is the link.
(Other definitions for hunky-dory that I've seen before include "A-OK" , "Excellent - fine" , "In excellent condition" .)