Old tax benefit -- it helped, partly (5)
I believe the answer is:
tithe
'old tax' is the definition.
'tithe' can be an answer for 'tax' (historical tax paid to the church). I am not sure about the 'old' bit.
'benefit it helped partly' is the wordplay.
'partly' indicates a hidden word (part of the clue is used).
'TITHE' is hidden within 'benefit it helped'.
Can you help me to learn more?
(Other definitions for tithe that I've seen before include "10 per cent levy" , "One tenth - old church tax" , "church funding" , "Tenth of income given to church" , "Tax paid to church" .)