... backing it, The Church's Share (5)
I believe the answer is:
tithe
'backing' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.
'it ithe church's sharei' is the wordplay.
'TITHE' is hidden in amongst the letters.
However, I am unsure how this is indicated.
Can you help me to learn more?
(Other definitions for tithe that I've seen before include "Levy, originally worth one tenth" , "Former church tax" , "Levy of one tenth of something" , "church funding" , "10 per cent levy" .)