Minor engagement risks him getting twitchy (8)
I believe the answer is:
skirmish
'minor engagement' is the definition.
(I've seen this before)
'risks him getting twitchy' is the wordplay.
'getting' says to put letters next to each other.
'twitchy' is an anagram indicator (I've seen this in other clues).
'risks'+'him'='riskshim'
'riskshim' with letters rearranged gives 'SKIRMISH'.
(Other definitions for skirmish that I've seen before include "Minor period of fighting" , "Scrap" , "Minor engagement -- his smirk (anag)" , "Minor short-term fight" , "Short engagement" .)