Cancellation includes compartment (4)
I believe the answer is:
cell
'compartment' is the definition.
(I know that cell is a type of compartment)
'cancellation includes' is the wordplay.
'includes' indicates the answer is hidden within the clue.
'CELL' is hidden within 'cancellation'.
(Other definitions for cell that I've seen before include "Prisoner's accommodation" , "Place of incarceration in body unit" , "Microscopic unit of living matter" , "Monastic room" , "Unit of animal or plant structure" .)