Complex King of Thebes (7)
I believe the answer is:
oedipus
I believe this is a double definition.
'complex' is the first definition.
(Oedipus complex is an example)
'king of thebes' is the second definition.
(I've seen this before)
(Other definitions for oedipus that I've seen before include "Sort of complex" , "Theban king of legend" , "Mythological king who killed his father and married his mother" , "Mythical Greek king of Thebes" , "Old Greek king who killed his father and married his mother" .)