Swimmer displaying roughness if disturbed (11)

I believe the answer is:

surgeonfish

'swimmer' is the definition.
(surgeonfish is a kind of aquatic vertebrate)

'roughness if disturbed' is the wordplay.
'disturbed' indicates an anagram (the order of letters is disturbed).
'roughness'+'if'='roughnessif'
'roughnessif' anagrammed gives 'SURGEONFISH'.

'displaying' acts as a link.

I've seen this clue in The Times.

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