Fight supporter with tip of lance (5)
I believe the answer is:
brawl
'fight' is the definition.
(I know that brawl is a type of fight)
'supporter with tip of lance' is the wordplay.
'supporter' becomes 'bra' (a bra gives support to breasts).
'with' becomes 'w' (short for with).
'tip of' indicates taking the first letters.
The first letter of 'lance' is 'l'.
'bra'+'w'+'l'='BRAWL'
(Other definitions for brawl that I've seen before include "Ruckus" , "Quarrel noisily" , "Rough, noisy fight" , "Rowdy fight" , "Scuffle, unseemly fight" .)