Like a complex king’s gem worn by English princess? (7)
I believe the answer is:
oedipal
'like a complex king's' is the definition.
(like King Oedipus who inspired the Oedipus complex)
'gem worn by english princess?' is the wordplay.
'gem' becomes 'opal' (opal is a kind of gem).
'worn by' indicates putting letters inside (I've seen this in other clues).
'english' becomes 'e' (abbreviation).
'princess?' becomes 'di'.
'e'+'di'='edi'
'opal' going around 'edi' is 'OEDIPAL'.
(Other definitions for oedipal that I've seen before include "Relating to a son/mother complex" , "Of legendary king of Thebes" , "type of conflict arising in Greece" , "Type of complex" , "Like a boy desiring his mother" .)