Theatre cancels trailer for Boys Night (4)

I believe the answer is:

stag

I'm a little stuck... Click here to teach me more about this clue!

'night' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for stag that I've seen before include "without female escort" , "Male deer; speculator" , "Antlered beast" , "One who speculates" , "Share speculator" .)

I've seen this clue in the Sydney Morning Herald.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.