Permissible range of variation shown by the patient (9)

I believe the answer is:

tolerance

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

'permissible range' is the definition.
'tolerance' can be an answer for 'range' (thesaurus). I am not certain of the 'permissible' bit.

I can't explain the remainder of the clue.

Can you help me to learn more?

(Other definitions for tolerance that I've seen before include "ecumenical spirit?" , "Understanding" , "See 10" , "Indulgence" , "Amount of play" .)

I've seen this clue in The Irish Independent.

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