Penitent shortly continued with a ceremony (8)
I believe the answer is:
contrite
'penitent' is the definition.
(similar in meaning)
'shortly continued with a ceremony' is the wordplay.
'shortly continued' becomes 'cont' (common abbreviation; 'shortly' indicates an abbreviation).
'with' means one lot of letters go next to another.
'a ceremony' becomes 'rite' (rite is a kind of ceremony).
'cont'+'rite'='CONTRITE'
(Other definitions for contrite that I've seen before include "Feeling remorse" , "Penitent, feeling guilty" , "guilt-ridden" , "Repentant about nice trot" , "Repentant and chastened" .)