Swimmer's woe (5)
I believe the answer is:
cramp
'swimmer's woe' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for cramp that I've seen before include "restraint" , "Form of muscular pain" , "writers may be familiar with" , "Severe muscular pain" , "Involuntary muscular contraction" .)