Overwhelm rebels, lunge head first (6)
I believe the answer is:
engulf
'overwhelm' is the definition.
(I've seen this before)
'rebels lunge head first' is the wordplay.
'rebels' indicates anagramming the letters.
'head' suggests taking the first letters.
The first letter of 'first' is 'f'.
'lunge' is an anagram of 'engul'.
'engul'+'f'='ENGULF'
(Other definitions for engulf that I've seen before include "Flood" , "Lowered in rank" , "Swallow up, overwhelm" , "Overwhelm; cover totally" , "Absorb or overwhelm" .)