Great upset with a curtailed Mrs. Thatcher (8)
I believe the answer is:
margaret
'thatcher' is the definition.
(prime minister Margaret Thatcher)
'great upset with a curtailed mrs' is the wordplay.
'upset with' is an anagram indicator.
'curtailed' means to remove the last letter.
'mrs' with its final letter removed is 'mr'.
'a'+'mr'='amr'
'great' mixed up with 'amr' gives 'MARGARET'.
(Other definitions for margaret that I've seen before include "- Rutherford, actress" , "-- Drabble, writer" , "Woman" , "That great charmer (anag) -- politician" , "Princess and Thatcher" .)