Rocks caught in chimney glow (9)
I believe the answer is:
fluoresce
'glow' is the definition.
(fluorescing is a kind of glowing)
'rocks caught in chimney' is the wordplay.
'rocks' becomes 'ores' (I've seen this before).
'caught' becomes 'c' (cricket abbreviation).
'in' is an insertion indicator.
'chimney' becomes 'flue' (I've seen this before).
'ores'+'c'='oresc'
'oresc' inserted within 'flue' is 'FLUORESCE'.
(Other definitions for fluoresce that I've seen before include "Emit light when irradiated" , "glow brightly" .)