Trick rather obvious? Sorry! (8)
I believe the answer is:
contrite
'sorry' is the definition.
(synonyms)
'trick rather obvious?' is the wordplay.
'trick' becomes 'con' (a con is a fraud or trick).
'rather obvious?' becomes 'trite' (trite can mean obvious or banal).
'con'+'trite'='CONTRITE'
(Other definitions for contrite that I've seen before include "Suffering remorse" , "Feeling remorse" , "Wholly penitent" , "Regretful" , "Repentant and chastened" .)