A measure of familiarity (3)

I believe the answer is:

mil

'a measure' is the definition.
(mil is a kind of measure)

'of familiarity' is the wordplay.
'of' says the answer is hidden in the clue.
'MIL' is hidden within 'familiarity'.

(Other definitions for mil that I've seen before include "One thousandth of an inch" , "One thousanth of an inch" , "One / one thousand inch" , "tiny distance" .)

I've seen this clue in the Evening Standard.

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