be down to (do something)
To be ready, willing, or eager to do something. I'm down to play a quick game of soccer if you are. I am so down to see that movie tonight, I've been waiting for it to come out for months! A: "You want in?" B: "Yeah, I'm down."
be down to something
COMMON If something is down to something else, the second thing is the cause of the first. When you are asked to score goals, then a lot is down to confidence and Kevin has that. I think that the show's popularity is down to two things.
be down to something
have nothing except one or a few items of the kind mentioned: I’m down to my last penny.