Measure time sitting in meeting places (11)

I believe the answer is:

centimetres

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'places' is the definition.
Although both the answer and definition are plural nouns, I can't understand how one could define the other.

'measure time sitting in' is the wordplay.
'measure' becomes 'centres' (I can't justify this - if you can you should believe this answer much more).
'sitting in' indicates putting letters inside.
'centres' placed around 'time' is 'CENTIMETRES'.

'meeting' acts as a link.

Can you help me to learn more?

(Another definition for centimetres that I've seen is " measures".)

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

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