Tax benefit - it helps, to an extent (5)
I believe the answer is:
tithe
'tax' is the definition.
(thesaurus)
'benefit it helps to an extent' is the wordplay.
'to an extent' says the answer is hidden in the clue.
'TITHE' is hidden in the letters of 'benefit it helps'.
(Other definitions for tithe that I've seen before include "property tax" , "Tenth of income given to church" , "Church payment" , "One-tenth of income paid to church" , "Source of church revenue" .)