It rises with the old church tax (5)
I believe the answer is:
tithe
'old church tax' is the definition.
(I've seen this before)
'it rises with the' is the wordplay.
'rises' says the letters should be written in reverse.
'with' says to put letters next to each other.
'it' in reverse letter order is 'ti'.
'ti'+'the'='TITHE'
(Other definitions for tithe that I've seen before include "Tax paid to church" , "10% tax" , "One tenth - old church tax" , "property tax" , "Tenth part once paid as tax" .)