One watching rook, lone, confused (8)

I believe the answer is:

onlooker

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

'one watching' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.

'rook lone confused' is the wordplay.
'confused' indicates anagramming the letters.
'rook'+'lone'='rooklone'
'rooklone' with letters rearranged gives 'ONLOOKER'.

Can you help me to learn more?

(Other definitions for onlooker that I've seen before include "Witness" , "He's not involved - just observing" , "Person watching" , "Non-participant" , "Non-participating observer" .)

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.