Time to embrace revolutionary left’s rank (7)
I believe the answer is:
echelon
'rank' is the definition.
(I know that echelon is a type of rank)
'time to embrace revolutionary left's' is the wordplay.
'time' becomes 'eon' (eon is a kind of time).
'to embrace' means one lot of letters goes inside another.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'left' becomes 'l' (common abbreviation).
'che'+'l'='chel'
'eon' enclosing 'chel' is 'ECHELON'.
(Other definitions for echelon that I've seen before include "Grade or level" , "Body of troops arranged in a line" , "Military stepped formation" , "Offset-lines formation" , "Level of people in organisation" .)