Minor explosion — after a time, I go away (7)
I believe the answer is:
atishoo
'minor explosion' is the definition.
(noise of a sneeze)
'a time i go away' is the wordplay.
'time' becomes 't' (abbreviation).
'go away' becomes 'shoo' (I've seen this before).
'a'+'t'+'i'+'shoo'='ATISHOO'
'after' is the link.
(Other definitions for atishoo that I've seen before include "report of involuntary escape from trap?" , "hay-fever sufferer may interject this" , "25 sound" , "Sound of a sneeze" , "Sudden eruption" .)