Told leader about ketamine trip (4)

I believe the answer is:

trek

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

'trip' is the definition.
(I know that trek is a type of trip)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for trek that I've seen before include "A long arduous walk" , "Great journey" , "Long hard journey on foot" , "Long and difficult journey" , "A long arduous journey as in S Africa" .)

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.