Problem – broken tooth (4)
I believe the answer is:
snag
I believe this is a double definition.
'problem' is the first definition.
(snag can mean a problem or difficulty)
'broken tooth' is the second definition.
(I've seen this in another clue)
(Other definitions for snag that I've seen before include "Minor hitch" , "Sang about obstacle" , "A hidden or unexpected obstacle" , "Catch - disadvantage" , "Minor problem" .)