Angry swimmer out of the race (5)
I believe the answer is:
ratty
'angry' is the definition.
(thesaurus)
'swimmer out of the race' is the wordplay.
'swimmer' becomes 'ray' (ray is a kind of aquatic vertebrate).
'out of' indicates putting letters inside.
'the race' becomes 'tt'.
'ray' going around 'tt' is 'RATTY'.
(Other definitions for ratty that I've seen before include "Character created by Kenneth Grahame" , "Bad-tempered, irritable as a rodent" , "Fictional mole's chum" , "Irritable (colloq.)" , "Short" .)