Withdraw due to a slight injury (7)
I believe the answer is:
scratch
I believe this is a double definition.
'withdraw' is the first definition.
(I know this)
'a slight injury' is the second definition.
(I've seen this before)
'due to' acts as a link.
(Other definitions for scratch that I've seen before include "cash" , "Score a surface" , "Write hurriedly" , "Mark made by sharp point" , "small injury" .)