Dependent theme (7)
I believe the answer is:
subject
I believe this clue is a double definition.
'dependent' is the first definition.
(I know that dependent can be written as subject)
'theme' is the second definition.
(I know that theme can be written as subject)
(Other definitions for subject that I've seen before include "Citizenship' at school maybe" , "Topic being discussed" , "Person under 26?" , "person photographed" , "Subordinate - part of sentence" .)