Girl left in to block revolutionary (7)
I believe the answer is:
blanche
'girl' is the definition.
'left in to block revolutionary' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' means one lot of letters goes inside another.
'to block' becomes 'ban' (I've seen this in another clue).
'revolutionary' becomes 'Che' (Che Guevara the Marxist revolutionary).
'l' put within 'ban' is 'blan'.
'blan'+'che'='BLANCHE'
(Other definitions for blanche that I've seen before include "- of Castile was Queen to Louis VIII of France" , "- DuBois (Streetcar Named Desire)" , "Name of woman" , "Girl" , "Female" .)