Reserve force with revolutionary goal, keeping one illuminated (7)
I believe the answer is:
militia
'reserve force' is the definition.
(civilian military group)
'revolutionary goal keeping one illuminated' is the wordplay.
'revolutionary' shows that the letters should be reversed in order.
'goal' becomes 'aim' (aim is a kind of goal).
'keeping' indicates putting letters inside.
'one' becomes 'i' (Roman numeral).
'illuminated' becomes 'lit' (synonyms).
'aim' backwards is 'mia'.
'i'+'lit'='ilit'
'mia' placed around 'ilit' is 'MILITIA'.
'with' is the link.
(Other definitions for militia that I've seen before include "Civilian soldier force" , "Group of citizen soldiers" , "Civilian fighting force" , "Territorial force" , "Reservists" .)