Yep, we have no choice if someone wants to meet his clause and he wants to go.
However, assuming the clause is minimum £20m, then no Championship team has ever paid that much and the highest was Burnley this window (making the Mike Tresor loan permanent from last season, maybe an obligation to buy, but essentially a Premier League signing of £16m) and Wolves when they went a bit crazy splashing the cash on Ruben Neves for £16m and a few other teams buying players for around the £15m mark, so while Hamer might very well go on deadline day, I doubt it will be to Leeds (altho they have a lot of cash coming in so who knows)