Tax whisky, not the Church (4)
I believe the answer is:
scot
'tax' is the definition.
(thesaurus)
'whisky not the church' is the wordplay.
'whisky' becomes 'scotch' (Scotch is an example).
'not' suggests deleting specific letters.
'the church' becomes 'ch' (common abbreviation).
'scotch' with 'ch' taken away is 'SCOT'.
(Other definitions for scot that I've seen before include "Highlander, for example" , "Highlander, say" , "Glaswegian, say" , "Highlander perhaps" , "Northerner; old tax" .)