Under the influence of Morpheus? (6)

I believe the answer is:

drowsy

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

'under' is the definition.
Both the answer and definition are adjectives. Maybe you can see an association between them that I don't see?

I don't understand the remainder of the clue.

Can you help me to learn more?

(Other definitions for drowsy that I've seen before include "Dull" , "Half asleep" , "Soporific" , "Comatose" , "Not being very alert" .)

I've seen this clue in the Evening Standard.

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.