Actor involved with prison plotter (11)
I believe the answer is:
conspirator
'plotter' is the definition.
(I know that plotter can be written as conspirator)
'actor involved with prison' is the wordplay.
'involved with' is an anagram indicator (involved can mean confusing or complex).
'actor' with its letters anagrammed with 'prison' makes 'CONSPIRATOR'.
(Other definitions for conspirator that I've seen before include "Secret plotter" , "Person who secretly plots with others" , "Planner in secret" .)