Tax being cut (6)

But I've got no explanation for this one! Could you help me understand?
(Other definitions for really that I've seen before include "Honestly, it's a fact" , "surprised expression" , "Dead" , "Well I never!" , "as a matter of fact" .)
I believe this clue is a double definition.
'tax' is the first definition.
(excise is a kind of tax)
'cut' is the second definition.
(I've seen this in other clues)
'being' acts as a link.
(Other definitions for excise that I've seen before include "Remove by cutting out" , "A tax to be cut out, perhaps" , "Tax on certain goods and commodities" , "Expunge the tax?" , "that wretches hatefully collect" .)
