Racism - it forms a weapon (8)
I believe the answer is:
scimitar
'a weapon' is the definition.
(scimitar is a kind of weapon)
'racism it forms' is the wordplay.
'forms' indicates anagramming the letters.
'racism'+'it'='racismit'
'racismit' with letters rearranged gives 'SCIMITAR'.
(Other definitions for scimitar that I've seen before include "sharp weapon" , "Short curved oriental sword" , "I'm racist, owning an oriental sword" , "This cut" , "Type of sword with curved blade" .)