The swimmer sat around quietly at the far end (5)
I believe the answer is:
sprat
'the swimmer' is the definition.
(sprat is a kind of fish)
'sat around quietly at the far end' is the wordplay.
'around' indicates putting letters inside.
'quietly' becomes 'p' (musical symbol).
'at' is a charade indicator (letters next to each other).
'end' indicates one should take the final letters.
The last letter of 'far' is 'r'.
'p'+'r'='pr'
'sat' placed around 'pr' is 'SPRAT'.
(Other definitions for sprat that I've seen before include "Young herring" , "Type of herring - small person or thing" , "Small fish, sardine, say" , "It's set to catch a mackerel" , "Strap up the small fish" .)