Article about Middle East setback? That’s the idea (5)
I believe the answer is:
theme
'the idea' is the definition.
(theme is a kind of idea)
'article about middle east setback?' is the wordplay.
'article' becomes 'the' (the definite article in English).
'about' is an insertion indicator.
'middle east' becomes 'me' (abbreviation for Middle East).
'setback?' says the letters should be written backwards (I've seen 'setback' mean this).
'me' written backwards gives 'em'.
'the' going around 'em' is 'THEME'.
'that's' acts as a link.
(Other definitions for theme that I've seen before include "Topical item" , "Motif that's repeated" , "Subject (of talk, text, etc)" , "Recurrent unifying idea" , "subject,motif" .)