Aunties swimming in Serpentine (7)

I believe the answer is:

sinuate

'serpentine' is the definition.
(thesaurus)

'aunties swimming' is the wordplay.
'swimming' indicates anagramming the letters (letters swim around into a new order).
'aunties' anagrammed gives 'SINUATE'.

'in' is the link.

(Another definition for sinuate that I've seen is " With a wavy margin (botany); sea unit (anag.)".)

I've seen this clue in The Guardian.

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