If 'Leader' is coded as 'Actor', 'Actor' as an 'Administrator', 'Administrator' as a 'Traitor', 'Traitor' as a 'Social-reformer', then who takes part in the Parliamentary elections?

Actor

As a leader is coded as an actor and a leader takes part in the election the answer would be "Actor".

Don't get confused that an actor is further coded as something. We have to stick to what is being asked in the question. It is asking about the leader and the leader is coded as an actor and that is the final answer.