If the clue was 'Reimbursed', then REPAID would answer it perfectly. The only other alternative, as you say, is REWARD, but reimbursement carries the specific sense of a financial settlement to cover loss or expenditure, while a reward is given in return for something that takes a different form (eg money for a service, a prize for a performance).
However, the clue clearly indicates a noun, and thus in the absence of any additional information the expected answer must be REWARD.