Plot angle overwhelms faint-hearted swimmer (5,4)

I believe the answer is:

pilot fish

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'swimmer' is the definition.
Both the definition and answer are singular nouns.
Maybe there's an association between them I don't understand?

'plot angle overwhelms faint-hearted' is the wordplay.
'angle' becomes 'fish' (synonyms).
'overwhelms' means one lot of letters goes inside another.
'hearted' says to take the centre.
The middle of 'faint' is 'i'.
'plot'+'fish'='plotfish'
'plotfish' going around 'i' is 'PILOT-FISH'.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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