Subjects about right for the Torrid Zone (7)
I believe the answer is:
tropics
'the torrid zone' is the definition.
('tropics' can be a synonym of 'torrid zone')
'subjects about right' is the wordplay.
'subjects' becomes 'topics' ('topic' can be a synonym of 'subject').
'about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'topics' enclosing 'r' is 'TROPICS'.
'for' acts as a link.
(Other definitions for tropics that I've seen before include "hot spots" , "Cancer, Capricorn" , "hot regions" , "Region either side of equator" , "hot spot" .)