Eternity embracing revolutionary left position (7)
I believe the answer is:
echelon
'position' is the definition.
(thesaurus)
'eternity embracing revolutionary left' is the wordplay.
'eternity' becomes 'eon' (I've seen this before).
'embracing' indicates putting letters inside.
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'left' becomes 'l' (common abbreviation).
'che'+'l'='chel'
'eon' going around 'chel' is 'ECHELON'.
(Other definitions for echelon that I've seen before include "Rank - status" , "Military stepped formation" , "Military row formation" , "Leech on (anag.)" , "Level or rank of authority, upper or lower" .)