Extremely good-looking NI footballer keeps playing there (8)

I believe the answer is:

bonniest

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

'playing there' is the definition.
I can't tell whether this defines the answer.

'extremely good-looking ni footballer keeps' is the wordplay.
'extremely good looking' becomes 'on' (I am not sure about this - if you are sure you should believe this answer much more).
'footballer' becomes 'Best' (George Best, o946-n005).
'keeps' means one lot of letters goes inside another (inserted letters are kept inside).
'on'+'ni'='onni'
'onni' put into 'best' is 'BONNIEST'.

Can you help me to learn more?

(Another definition for bonniest that I've seen is " Most healthy-looking baby".)

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.