Turn fan backwards and ventilate after evacuation (7)

I believe the answer is:

revolve

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

'turn' is the definition.
(to revolve is to turn around)

I cannot understand how the remainder of the clue works.

(Other definitions for revolve that I've seen before include "Turn around" , "Rotate" , "Turn round" , "Go round" , "Pirouette" .)

I've seen this clue in The Times.

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.