Choice of third of elders in church (6)
I believe the answer is:
select
'choice' is the definition.
(I know that choice can be written as select)
'third of elders in church' is the wordplay.
'third of elders' becomes 'le' (I can't justify this - if you can you should give a lot more credence to this answer).
'in' indicates putting letters inside.
'church' becomes 'sect' (sect is a kind of church).
'le' placed into 'sect' is 'SELECT'.
'of' is the link.
Can you help me to learn more?
(Other definitions for select that I've seen before include "Pick among chosen group" , "Choose - choice" , "'Choose, pick out (6)'" , "Single out" , "Exclusive, admitting only certain people" .)