Imminent night manoeuvre - almost a disaster (4,5)
I believe the answer is:
near thing
'almost a disaster' is the definition.
(I've seen this before)
'imminent night manoeuvre' is the wordplay.
'imminent' becomes 'near' (I've seen this in another clue).
'manoeuvre' is an anagram indicator.
'night' is an anagram of 'thing'.
'near'+'thing'='NEAR THING'
(Other definitions for near thing that I've seen before include "Narrow escape, close shave" , "Even the short-sighted could plainly see that" , "Narrow escape, missed by a small margin (4.5)" , "Something that barely avoids failure or disaster" , "almost a disaster" .)