Chambers (5)
(Other definitions for cells that I've seen before include "Dungeons" , "Small rooms" , "terrorist groups" , "Basic structural units of all organisms" , "Accommodation for prisoners" .)
'chambers' is the definition.
(I know this)
This is all the clue.
(Other definitions for rooms that I've seen before include "Lodgings" , "Chambers" , "Rented suite" , "Areas in a building" , "Partitioned parts of a building" .)