Sudden outburst (5-2)
I believe the answer is:
flare-up
'sudden outburst' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for flare-up that I've seen before include "Burst into flames" , "Sudden outbreak (of violence, etc)" , "Suddenly get angry" , "Explosion of emotion" , "Suddenly burn brightly" .)