Bit of compartment (4)

I believe the answer is:

part

I believe this is a double definition.

'bit of' is the first definition.

'compartment' is the second definition.
(thesaurus)

(Other definitions for part that I've seen before include "Portion, segment" , "Section of a whole" , "Constituent - something to play?" , "Region" , "Separate - role" .)

I've seen this clue in The Mirror.

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