Right molar’s erupting (5)
I believe the answer is:
moral
'right' is the definition.
(similar in meaning)
'molar's erupting' is the wordplay.
'erupting' is an anagram indicator.
'molar' with letters rearranged gives 'MORAL'.
(Other definitions for moral that I've seen before include "Relating to good and evil" , "Underlying significance of a story or event" , "Lesson that can be drawn from a story" , "Virtuous and principled" , "knowing right from wrong" .)