Cellar chamber contains vault (4)
I believe the answer is:
arch
'vault' is the definition.
(thesaurus)
'cellar chamber contains' is the wordplay.
'contains' indicates the answer is hidden within the clue.
'ARCH' is hidden within 'cellar chamber'.
(Other definitions for arch that I've seen before include "Affectedly playful (4)" , "Curvature" , "Affectedly playful like curved structure" , "Self-consciously playful or teasing" , "Chief - supporter - cunning" .)