Regret some tremors eventually (7)
I believe the answer is:
remorse
'regret' is the definition.
(remorse is a feeling of regret)
'some tremors eventually' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'REMORSE' is hidden within 'tremors eventually'.
(Other definitions for remorse that I've seen before include "Regret or sorrow for wrong-doing" , "Guilty conscience" , "it may bite" , "Distress from a sense of guilt" , "Guilt for a wrong deed" .)