Outside of folding preflop, and folding on the flop....

I would just call on the turn. You've now picked up so much equity with the 4th club. If villain does have an ace and decides to 3-bet, you might need to fold your hand now. I'd just call turn and hit your flush 20% of the time.

Edit: I realize you called the flop with the intention to bluff on the turn, but after you pick up a flush draw on the turn I think it is best to change plans (unless your are very sure villain can be moved off of their hand.