River in question's somewhere near the Equator (7)
I believe the answer is:
tropics
'somewhere near the equator' is the definition.
(the tropics are near the equator)
'river in question's' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'in' means one lot of letters goes inside another.
'question's' becomes 'topic's' (both can mean a particular subject).
'r' placed into 'topics' is 'TROPICS'.
(Other definitions for tropics that I've seen before include "hot spot" , "heated situations" , "Cancer, Capricorn" , "Region either side of equator" , "hot regions" .)