Staff initially push for increase (5)
I believe the answer is:
surge
'increase' is the definition.
(I know that surge is a more specific form of the action blow up)
'staff initially push for' is the wordplay.
'initially' indicates taking the first letters.
'push for' becomes 'urge' (I've seen this in another clue).
The first letter of 'staff' is 's'.
's'+'urge'='SURGE'
(Other definitions for surge that I've seen before include "Rise suddenly" , "Sudden flow" , "Sudden rush" , "Rapid increase; powerful movement" , "Eddy" .)