This hand was played a while ago, so I don't recall any reads I may have had. I think BTN is a likely rec.

The main point I want to ask is: does this bet make sense?

If it was a heads-up pot, I would check my middle pair here. But I wanted to thin out the field a bit a bit here, because middle pair is rather vulnerable to getting outdrawn.

If I bet and get raised, what do I do? I think I have to call and evaluate turn.

I face a half pot bet on the turn. I decide to call because:

I don't block the FD, any backdoor FD or SD.
He could have been bluffing with overcards like suited broadways, which I don't block either.

On the con side: I do block some Ace-highs, but these hands might be inclined to check turn because they have some SDV. It might even be a good thing to have an Ace blocker, because he's more likely to bet turn with A9 than, say, J9.