River flowing through scrubland where fire started (6)
I believe the answer is:
hearth
'where fire started' is the definition.
(a hearth is a fireplace)
'river flowing through scrubland' is the wordplay.
'river' becomes 'r' (abbreviation for river).
'flowing through' indicates putting letters inside.
'scrubland' becomes 'heath' (I've seen this before).
'r' placed within 'heath' is 'HEARTH'.
(Other definitions for hearth that I've seen before include "Area around the fire" , "suitable place for a fire" , "Floor around fireplace" , "cosy setting" , "Fireplace surround" .)