If i close a gate and as part of the same other world encounter i gain a clue can i use that clue to advance the mystery or is the gate considered closed and finished with before I get the clue?

Mind posting the text of the mystery?

Omen of Devastation says that an investigator that closes a gate that corresponds to the current omen track can spend 1 clue to put one eldritch token on the card.​

I didn't have the clue when I closed the gate but a follow on test in the same encounter gave me a clue.

Ok, thanks. I'd rule that nope, you're not allowed. If the mystery specifies that you are allowed to spend 1 clue when you close the gate, then that's the specific time trigger: anything that happens after closing the gate, happens too late

Ok thanks