Keeps apart and is outside so long after hours (8)

I believe the answer is:

isolates

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'keeps apart' is the definition.
('isolate' can be a synonym of 'keep apart')

'is outside so long after hours' is the wordplay.
'outside' is an insertion indicator.
'long after hours' becomes 'late' (I can't explain this - if you can you should give a lot more credence to this answer).
'so'+'late'='solate'
'is' placed around 'solate' is 'ISOLATES'.

'and' is the link.

Can you help me to learn more?

(Other definitions for isolates that I've seen before include "Sets apart from others" , "Keeps apart from others" , "Places apart or alone" , "Oils seat (anag.)" .)

I've seen this clue in the Sydney Morning Herald.

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