Ships circling large swells (6)
I believe the answer is:
Here is my best explanation:
'swells' is the definition.
(bloating is a kind of swelling)
'ships circling large' is the subsidiary indication.
'ships' becomes 'boats'.
'circling' indicates putting letters inside (circling can mean going around or containing).
'large' becomes 'l'.
'boats' placed around 'l' is 'bloats'.