No, he can’t defer the offer unfortunately. It's one UCAS application per year, the year of application covers all university/course choices. If he doesn't get accepted by his CF university, he can decline his CI and go into Clearing. If there's nothing he likes for 2020 admission, he can withdraw from the 2020 UCAS cycle and apply again through UCAS for 2021 admission. The only other thing he could do is to ask both his CF and CI if they will allow him to defer entry until 2021. There's no reason to expect them to agree to do this and they could change the offer.