Issue — theme (5)
I believe the answer is:
topic
I believe this clue is a double definition.
'issue' is the first definition.
(I know that issue can be written as topic)
'theme' is the second definition.
(I know that theme can be written as topic)
(Other definitions for topic that I've seen before include "Issue (for discussion)" , "Talking point" , "Subject (eg, of text)" , "Subject (of a talk, etc)" , "Subject matter of a conversation or discussion" .)