Guess posted at a gate, in brief Crossword Clue

 The answer to the crossword clue "Guess posted at a gate, in brief" is ETD. It stands for Estimated Time of Departure.

This is a common clue in cryptic crosswords, where the answer is hidden in the clue itself. In this case, the word "guess" is a homophone of "ETD", and the word "posted" can be interpreted as "written" or "displayed".

Here are some other possible answers for the crossword clue "Guess posted at a gate, in brief":

PASS

EXIT

DOOR

GATE

BARRIER

The specific answer that is correct will depend on the context of the crossword puzzle.