Strip off like a swimmer, on the quiet (4)
I believe the answer is:
peel
'strip off' is the definition.
(thesaurus)
'a swimmer on the quiet' is the wordplay.
'a swimmer' becomes 'eel' (eel is a kind of aquatic vertebrate**).
'on' says to put letters next to each other.
'the quiet' becomes 'p' (music symbol for 'piano').
'eel' put after 'p' is 'PEEL'.
'like' acts as a link.
(Other definitions for peel that I've seen before include "A PM; a fortified tower" , "Strip the skin off" , "Flake" , "Shed skin" , "Remove skin of vegetable or fruit" .)