I am critical of limiting old quarantine (7)

I believe the answer is:

isolate

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'quarantine' is the definition.
(I've seen this before)

'i am critical of limiting old' is the wordplay.
'i am critical of limiting' becomes 'iso' (I can't explain this - if you can you should believe this answer much more).
'old' becomes 'late' (I've seen this in other clues).
'iso'+'late'='ISOLATE'

Can you help me to learn more?

(Other definitions for isolate that I've seen before include "Also tie (anag.)" , "Strand" , "Place in seclusion" , "Place apart from others or alone" , "Eat soil (anag)" .)

I've seen this clue in The Independent.

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