Of legendary king of Thebes (7)
I believe the answer is:
oedipal
'of legendary king of thebes' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for oedipal that I've seen before include "Like a boy desiring his mother" , "Type of complex" , "Relating to a son/mother complex" , "Like a complex" , "type of conflict arising in Greece" .)