Poke in the bottom leads to smack — that's a cold response! (9)

I believe the answer is:

goosebump

'that's a cold response' is the definition.
(goosebumps can be a response to cold)

'poke in the bottom leads to smack' is the wordplay.
'poke in the bottom' becomes 'goose' (goose can informally mean to poke in the bottom).
'leads to' is a charade indicator (letters next to each other).
'smack' becomes 'bump' (both can mean to hit or smash).
'goose'+'bump'='GOOSEBUMP'

I've seen this clue in The Guardian.

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