Popular protest about unpleasant person in charge (10)
I believe the answer is:
democratic
'popular' is the definition.
('democratic' can be similar in meaning to 'popular')
'person in charge' is the wordplay.
'person' becomes 'democrat' (democrat is a kind of person**).
'in charge' becomes 'ic'.
'democrat'+'ic'='DEMOCRATIC'
'protest about unpleasant' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for democratic that I've seen before include "party in US" , "Popular" , "Enabling the will of the people" , "23 [JFK] was" , "Egalitarian" .)