Small room (6)
'small room' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cell that I've seen before include "Compartment in honeycomb" , "Small room for confining a prisoner" , "Where a prisoner is kept" , "Spreadsheet unit" , "Prisoner's accommodation" .)
(Other definitions for closet that I've seen before include "Confine" , "Furtive" , "small compartment for clothing" , "Secret - cupboard" , "secret is revealed" .)