Sailor poles in lakes (5)

I believe the answer is:

tarns

'lakes' is the definition.
(I know this)

'sailor poles' is the wordplay.
'sailor' becomes 'tar' (slang term for a sailor).
'poles' becomes 'NS' (north and south poles).
'tar'+'ns'='TARNS'

'in' acts as a link.

(Another definition for tarns that I've seen is " Mountain lakes".)

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

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