Girl closes hackneyed religious ceremony (4,5)
I believe the answer is:
last rites
'religious ceremony' is the definition.
(last rites is a kind of religious ceremony)
'girl closes hackneyed' is the wordplay.
'girl' becomes 'lass' (lass is a kind of girl).
'closes' is an insertion indicator (inserted letters are closed or sealed in).
'hackneyed' becomes 'trite' (synonyms).
'lass' placed around 'trite' is 'LAST RITES'.
(Other definitions for last rites that I've seen before include "Those near death may be given these" , "final service, maybe" , "Final ceremony" , "Starlet is having final sacraments before death" , "Final ceremonies for the dying" .)