From there, afterwards, to church (6)
I believe the answer is:
'from there' is the definition.
(I've seen this in another clue)
'afterwards to church' is the wordplay.
'afterwards' becomes 'then' (I've seen this in another clue).
'to church' becomes 'CE' (abbreviation for Church of England).
(Other definitions for thence that I've seen before include "As a consequence" , "from that time" , "From that point" , "It follows" , "From that place" .)