Board aircraft, your Majesty, but don't carry drug! (5)

I believe the answer is:

plank

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

'board' is the definition.
(I know that board can be written as plank)

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for plank that I've seen before include "Building timber" , "item in political party's programme" , "Policy; board" , "Long piece of wood" , "Wooden board" .)

I've seen this clue in The Independent.

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.