Notice wife plunging into warmer stream (9)

I believe the answer is:

headwater

'stream' is the definition.
(I've seen this before)

'notice wife plunging into warmer' is the wordplay.
'notice' becomes 'ad' (short for advert).
'wife' becomes 'w'.
'plunging into' is an insertion indicator (I've seen this in other clues).
'warmer' becomes 'heater' (synonyms).
'ad'+'w'='adw'
'adw' put within 'heater' is 'HEADWATER'.

(Another definition for headwater that I've seen is " stream".)

I've seen this clue in The Times.

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