Cigar with a revolutionary source (7)
I believe the answer is:
cheroot
'cigar' is the definition.
(cheroot is a kind of cigar)
'with a revolutionary source' is the wordplay.
'with' says to put letters next to each other.
'a revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'source' becomes 'root' (both can mean the origin of something).
'che' next to 'root' is 'CHEROOT'.
(Other definitions for cheroot that I've seen before include "Small cigar" , "Cigar cut at both ends" , "With both ends cut off squarely, is smoked" , "Cigar with ends squarely removed" , "Havana?" .)