Reactionary corrupts a pioneering MP (5)
I believe the answer is:
astor
'pioneering mp' is the definition.
I can't tell whether this definition defines the answer.
'reactionary corrupts a' is the wordplay.
'reactionary' says the letters should be written backwards (reactions happen in the opposite direction).
'corrupts' becomes 'rots' (I've seen this in another clue).
'rots'+'a'='rotsa'
'rotsa' back-to-front is 'ASTOR'.
Can you help me to learn more?
(Other definitions for astor that I've seen before include "First woman to sit in the House of Commons, d. 1964" , "First female MP" , "female parliamentarian" , "Female politician" , "Nancy ---, first woman MP" .)