Sword: it stops racism developing (8)
I believe the answer is:
scimitar
'sword' is the definition.
(scimitar is a kind of sword)
'it stops racism developing' is the wordplay.
'stops' is an insertion indicator (stopping can mean blocking a gap).
'developing' is an anagram indicator (letters developed into a new form).
'racism' with letters rearranged gives 'scimar'.
'it' going into 'scimar' is 'SCIMITAR'.
(Other definitions for scimitar that I've seen before include "Double-edged sword" , "Eastern sword" , "This cut" , "Sword with curved blade used by the Turks and Persians" , "Short curved oriental sword" .)