Snap, having volatile mentor thump foes (4-2-3-6)

I believe the answer is:

spur-of-the-moment

'snap' is the definition.
(I've seen this in another clue)

'volatile mentor thump foes' is the wordplay.
'volatile' indicates anagramming the letters.
'mentor'+'thump'+'foes'='mentorthumpfoes'
'mentorthumpfoes' with letters rearranged gives 'SPUR-OF-THE-MOMENT'.

'having' is the link.

I've seen this clue in The Times.

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