Swimmer a bit unfortunate to finish up in the can (4)

I believe the answer is:

tuna

I'm a little stuck... Click here to teach me more about this clue!

'swimmer' is the definition.
(tuna is a type of fish)

'a bit unfortunate to finish up in the can' is the wordplay.
'TUNA' is hidden in amongst the letters.
But, I'm uncertain how this is indicated.

Can you help me to learn more?

(Other definitions for tuna that I've seen before include "Fish; edible cactus" , "A fish; sounds like piano juster" , "Common food fish" , "Widely-eaten fish" , "Sea creature" .)

I've seen this clue in the Evening Standard.

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