Notes written here in Home Counties about tax return (5)
I believe the answer is:
stave
'notes written here' is the definition.
(musical notes are written on a stave)
'home counties about tax return' is the wordplay.
'home counties' becomes 'se' (Home Counties in the South East of England).
'about' means one lot of letters goes inside another.
'tax' becomes 'VAT' (British sales tax).
'return' shows that the letters should be reversed in order.
'vat' reversed gives 'tav'.
'se' placed around 'tav' is 'STAVE'.
'in' acts as a link.
(Other definitions for stave that I've seen before include "Set of lines on which musical notes are written" , "System of five horizontal lines in written music" , "Strip of wood" , "Bar" , "Wooden piece of barrel" .)