Sleep party ends with impetuous infant's complaint (5,4)

I believe the answer is:

nappy rash

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'infant's complaint' is the definition.
I know nothing about this answer so I can't tell whether this works.

'sleep party ends with impetuous' is the wordplay.
'sleep' becomes 'nap' (I've seen this before**).
'ends' says to hollow out the word (remove centre letters).
'with' says to put letters next to each other.
'impetuous' becomes 'rash' (I've seen this before).
'party' with its middle taken out is 'py'.
'nap'+'py'+'rash'='NAPPY RASH'

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(Other definitions for nappy rash that I've seen before include "wet spots" , "Baby's discomfort" .)

I've seen this clue in The Guardian.

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