Supporters rush finally forward (5)
I believe the answer is:
brash
'forward' is the definition.
('brash' can be similar in meaning to 'forward')
'supporters rush finally' is the wordplay.
'supporters' becomes 'bras' (I've seen this in other clues).
'finally' suggests the final letters.
The last letter of 'rush' is 'h'.
'bras'+'h'='BRASH'
(Other definitions for brash that I've seen before include "Foolhardy" , "Loud, garish" , "loose broken rock" , "Brazen" , "forward" .)