Rapid rise (7)
I believe the answer is:
upsurge
'rapid rise' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for upsurge that I've seen before include "A sudden rise, as in business" , "Sudden large increase" , "Hike" , "Sudden forceful flow from below" , "A sudden rise as in fortunes" .)