Unite after revolutionary gives ground (6)
I believe the answer is:
chewed
'ground' is the definition.
(chewing is a kind of grinding)
'unite after revolutionary' is the wordplay.
'unite' becomes 'wed' (wedding is a kind of uniting).
'after' is a charade indicator (letters next to each other).
'revolutionary' becomes 'che' (Che Guevara the Marxist revolutionary).
'wed' after 'che' is 'CHEWED'.
'gives' is the link.
(Other definitions for chewed that I've seen before include "Ground between teeth, say gum" , "Masticated, worked with teeth" , "Thought about" , "Made use of teeth" , "Masticated between teeth - maybe gum" .)