If it is clear from the buyers’ survey report that the buyers will have to do work on the property to deal with problems, you can agree to knock a certain amount off the price. That is what the buyer is often looking for. But the unscrupulous buyer is looking for a discount without any intention of doing any works.
If you are under strong pressure to compensate the buyers in some way, and you feel you need to do so, there are different approaches to take. You could agree to put right the defect yourself. That gives you some control over the cost, but you will suffer some disruption. It may not satisfy a buyer who will fear that you will go for the cheapest short-term solution.
You can agree to pay for the works carried out by the buyer after completion. That way at least you know you’re not being conned. But you then lack a certain amount of control over what works are done and at what expense. I would personally favour this strategy, but with the added precaution that you put an upper limit on the cost. The solicitors will agree a clause about this to go in the contract.
The buyers will probably want the anticipated cost to be deposited by you with the solicitors, with any balance coming back to you once the works are completed. (You wouldn’t be coming up with any cash directly. It would be coming out of the sale money the buyer will be paying you at completion.)