Strip off like a soft-headed swimmer! (4)
I believe the answer is:
peel
'strip off' is the definition.
(I've seen this before)
'soft-headed swimmer' is the wordplay.
'soft' becomes 'pp' (musical abbreviation for pianissimo).
'headed' means to remove the first letter (head can mean to remove the top from something).
'swimmer' becomes 'eel' (eel is a type of fish).
'pp' with its first letter taken away is 'p'.
'p'+'eel'='PEEL'
'like a' is the link.
(Other definitions for peel that I've seen before include "old prime minister" , "A PM; a fortified tower" , "Take skin off fruit" , "Remove skin from with blade" , "Outer fruit layer" .)