Ships circling large swells (6)

I believe the answer is:

bloats

'swells' is the definition.
(bloating is a kind of swelling)

'ships circling large' is the wordplay.
'ships' becomes 'boats'.
'circling' is an insertion indicator (circling can mean going around or containing).
'large' becomes 'l'.
'boats' placed around 'l' is 'BLOATS'.

I've seen this clue in The Telegraph.

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