Popular comrade upset by nervous twitch (10)
I believe the answer is:
democratic
'popular' is the definition.
('democratic' can be similar in meaning to 'popular')
'comrade upset by nervous twitch' is the wordplay.
'upset by' is an anagram indicator.
'nervous twitch' becomes 'tic' (I've seen this before).
'comrade' is an anagram of 'democra'.
'democra'+'tic'='DEMOCRATIC'
(Other definitions for democratic that I've seen before include "23 [JFK] was" , "Popular" , "Enabling the will of the people" , "Egalitarian" , "party in US" .)