Can you withhold arrears from VA Disability?
I'm going to go ahead and assume you're talking about child support. No, you can't withhold arrears from VA disability.
However, if the veteran obligor who has a disability rating falls behind in the obligation to timely pay child support and/or alimony, the obligee may file an apportionment request with VA and if VA agrees, they will withhold a portion of the disability money and send it directly to the obligee.
The apportionment request form is here and must be completed as the instructions say. Once VA receives the form they'll notify the veteran of the request and the vet will complete a financial statement. VA will usually make a decision within a few weeks. Good luck.