An item may be perfect when packing and posting, but couriers / postal services do not handle items with kid gloves, items do get broken in the post that's why these companies have compensation procedures.
You first need to refund your buyer. They need to open a case for item not as described, and accepting and refunding within 3 days, sees your seller performance not affected.
If you wish for the item to be sent back to you, you will need to pay for the tracked return postage and refund only when the item is back with you.
You can then, after refunding your buyer, try for compensation for yourself from the carrier used, for this broken item.
@marbr_7257