A celebrant converted in place of worship (10)
I believe the answer is:
tabernacle
'place of worship' is the definition.
(tabernacle is a kind of place of worship)
'a celebrant converted in' is the wordplay.
'converted' is an anagram indicator.
'in' indicates putting letters inside.
'celebrant' is an anagram of 'taberncle'.
'a' put into 'taberncle' is 'TABERNACLE'.
(Other definitions for tabernacle that I've seen before include "A celebrant (anag) - place of worship" , "sanctuary" , "Mormon temple" , "Mormon meeting-place" , "Tent for the Ark of the Covenant" .)