Self-satisfied with what’s holding the teeth back (4)
I believe the answer is:
smug
'self-satisfied' is the definition.
(synonyms)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for smug that I've seen before include "Superior" , "Self-satisfied, complacent" , "Conceited and self-satisfied" , "Self-righteously complacent" , "Full of oneself" .)