Unusually tart, I constantly scold revolutionary dramatist (8)
I believe the answer is:
rattigan
'dramatist' is the definition.
(playwright Terence Rattigan)
'unusually tart i constantly scold revolutionary' is the wordplay.
'unusually' is an anagram indicator.
'constantly scold' becomes 'nag' (to nag is to annoy or complain regularly).
'revolutionary' says the letters should be written backwards.
'nag' written backwards gives 'gan'.
'tart' with letters rearranged gives 'ratt'.
'ratt'+'i'+'gan'='RATTIGAN'
(Other definitions for rattigan that I've seen before include "Terence --, English playwright" , "20th-century playwright" , "Playfellow" , "Writer" .)