Tern — ocean's glory (3,7)

I believe the answer is:

sea swallow

'tern' is the definition.
(sea swallow is a kind of tern)

'ocean's glory' is the wordplay.
'ocean's' becomes 'sea's' ('sea' can be a synonym of 'ocean').
'glory' becomes 'wallow' (wallow can mean to glory in something).
'seas'+'wallow'='SEA-SWALLOW'

I've seen this clue in The Times.

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