Library? I presume you mean deck here.
Dominion rules require you to play all Treasure cards before buying any cards (buying from the Black Market excepted). This matters in games with Grand Market, Mint, and Mandarin. You can't, for example, play two Golds, buy a Grand Market, and then play some Coppers to pick something else up with an extra Buy.
So what that means for Clubhouse is that if you buy something with Clubhouse in play, thereby drawing an additional Treasure card into your hand, you can't then play that Treasure card.
You might be able to fix this by putting a Venture-style "play the Treasure card" clause in, but I can't be sure off-hand if that would be free of any rules conflicts with existing or future cards. I can't think of any problems off the top of my head, at least.