Do you mean what it says?
“Buyer to order appraisal within three business days.”
Buyers don’t order appraisals, lenders do. Buyers don’t necessarily control when the lender orders the appraisal. If you are the selling agent, do your clients really want the seller to terminate the transaction because the appraisal wasn’t ordered in the first three business days? And, if you are the listing agent, are you asking for proof that the appraisal was ordered? If not, why include the term in the first place? You won’t be able to terminate the contract if, two weeks into the escrow period, you find out the appraisal wasn’t ordered until the 7th day.
If you want to communicate the need to order the appraisal early due to the current appraisal delays, say this instead: Buyer will make every reasonable effort to cause the lender to order the appraisal of the property within three business days.
Your buyer can do this.