Fled before the start of the storm (4)
I believe the answer is:
rant
'storm' is the definition.
(both can mean to rage)
'fled before the start of the' is the wordplay.
'fled' becomes 'ran' (ran away).
'before' means one lot of letters go next to another.
'the start of' suggests taking the first letters.
The first letter of 'the' is 't'.
'ran'+'t'='RANT'
(Other definitions for rant that I've seen before include "Talk wildly and incoherently" , "Show anger" , "Shout wildly at length" , "Speak wildly and incoherently" , "End-of-course exams" .)