one that acts: a doer
one that takes part in a situation
(policy debate) One who enacts a certain policy action.
Latent publics are important in PR but Actors are not latent. There is knowledge and cognition in the human and social make-up of people that means that there is always a possibility of identifying tokens and values where there can be common ground. But sometimes these can be very difficult to find and the process may be long term to develop mutual values.
Thus there remains a group of actors available in as in Grunig's latent publics.
There is a need for actors to 'hold' tokens and values and thereby be a participant if only because of awareness within a social frame.
Actors are people.