Blow up general engaging in manoeuvres (7)
I believe the answer is:
enlarge
'blow up' is the definition.
('enlarge' can be a synonym of 'blow up')
'general engaging in manoeuvres' is the wordplay.
'engaging in manoeuvres' is an anagram indicator.
'general' is an anagram of 'ENLARGE'.
(Other definitions for enlarge that I've seen before include "Wax" , "Amplify" , "Make bigger in general" , "Widen" , "Make greater" .)