Attack with gun whilst I pop out (6-4)

I believe the answer is:

pistol-whip

'attack with gun' is the definition.
(hit someone with the butt of a pistol)

'whilst i pop out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'whilst'+'i'+'pop'='whilstipop'
'whilstipop' is an anagram of 'PISTOL-WHIP'.

I've seen this clue in The Times.

Want a hint initially instead of a full solution? Install my app