Fellows receiving unknown backing for church meeting (5)
I believe the answer is:
synod
'church meeting' is the definition.
(I've seen this in another clue)
'fellows receiving unknown backing' is the wordplay.
'fellows' becomes 'dons'.
'receiving' indicates putting letters inside.
'unknown' becomes 'y' (algebra).
'backing' says the letters should be written backwards.
'dons' going around 'y' is 'donys'.
'donys' written backwards gives 'SYNOD'.
'for' acts as a link.
(Other definitions for synod that I've seen before include "Council of bishops" , "Church council" , "Council of clergy to discuss policy" , "Ecclesiastical gathering" , "Ecclesiastical council" .)