My opinion is that it's more important from the perspective of the raiser to get calls from lesser hands than it is to price out a flush draw that probably isn't there.
With 2 clubs on the board there are 11 clubs left in the deck of 47 unseen cards. The chances any random hand has 2 clubs is (11/47*10/46) = 5.1%. While people are more likely to call raises with suited hands, they're also more likely to call raises with pairs, which are never suited... the effects probably cancelling out, so I'm only up against a flush draw about 1 time in 20.
That's why I tend to make my c-bets smaller than pot-size. There are only 2 Queens out and I want to get a call from a 7 or middle pair. It's also cheaper when I'm bluffing
and has a similar effect of getting "nothing" hands to fold.
Perhaps more interesting is what to do with your flush draw - do you call because you have good odds and some implied odds, or do you raise and hope to fold out a hand like AK?
I think it differs a lot depending on whether you're in a heads-up or multi-way pot.
1) If you're the only caller, I don't like this call pre-flop. A9s doesn't play well against a typical raising range. You should either fold or re-raise. (In this hand, AQo should fold to the re-raise. If he doesn't, you're shoving this flop/turn and have a fair amount of fold equity.) As played, raising is probably best because you fold out hands that didn't hit, and get hands like AQ to slow down and probably check the turn. Versus an overpair which isn't folding and may 3-bet this flop, you'd probably be facing a big bet you couldn't call on the turn anyway.
2) In a multi-way pot, calling is better because you're drawing to the nuts so want overcallers, and you have less fold equity.