Clue: Respite for swimmer boxing soldier (8)
Answer: BREATHER
Explanation: Definition: Respite
An envelope ('boxing') of RE ('soldier') in BATHER ('swimmer'). I have argued before for RE as 'soldier' singular, a person in the regiment (and placed after his name e.g. Captain Francis Fowke RE), as well as plural (as in 25A RECOUP), the whole regiment.