Grant to help defray costs (7)
I believe the answer is:
subsidy
'grant to help defray costs' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for subsidy that I've seen before include "Grant given to help with running costs" , "Grant paid to help with running costs" , "Arts grant, for example" , "Grant to help defray costs" , "Money granted to support an undertaking" .)