A huge shipping order? (5)

I believe the answer is:

avast

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

'shipping order?' is the definition.
The definition and answer are not the same part of speech.

'a huge' is the wordplay.
'huge' becomes 'vast' (I've seen this before).
'a'+'vast'='AVAST'

Can you help me to learn more?

(Other definitions for avast that I've seen before include "Stop (nautical)" , ""stop" signal" , "Stop on board" , "shout stopping the ship" , "Stop, nautically speaking" .)

I've seen this clue in The Irish News, The Guardian, The Globe and Mail, The Irish Independent and The Telegraph.

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.