Egalitarian party member in charge (10)
I believe the answer is:
democratic
'egalitarian' is the definition.
(similar in meaning)
'party member in charge' is the wordplay.
'party member' becomes 'democrat' (I've seen this before).
'in charge' becomes 'ic' (abbreviation for 'in charge').
'democrat'+'ic'='DEMOCRATIC'
(Other definitions for democratic that I've seen before include "Egalitarian" , "23 [JFK] was" , "Enabling the will of the people" , "party in US" , "Popular" .)