Baby, curiously, last to go in church (6)
I believe the answer is:
coddle
'baby' is the definition.
(synonyms)
'curiously last to go in church' is the wordplay.
'curiously' becomes 'oddly' (synonyms).
'last to go' means to remove the last letter (the last letter goes away).
'in' is an insertion indicator.
'church' becomes 'CE' (abbreviation for Church of England).
'oddly' with its final letter taken away is 'oddl'.
'oddl' inserted into 'ce' is 'CODDLE'.
(Other definitions for coddle that I've seen before include "Pamper -- cook in nearly boiling water" , "baby" , "Famous Dublin dish" , "Treat in an indulgent way" , "Cook in nearly-boiling water" .)