Back tooth (5)
I believe the answer is:
molar
'back tooth' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for molar that I've seen before include "Grinding tooth in the back of a mammal's mouth" , "Moral (anag.)" , "that could be capped" , "Chewer and grinder" , "Dealing with masses" .)