Old stove, bright colour (6)
I believe the answer is:
orange
'bright colour' is the definition.
(orange is a bright colour)
'old stove' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'stove' becomes 'range' (synonyms).
'o'+'range'='ORANGE'
(Other definitions for orange that I've seen before include "Name of reigning house of the Netherlands" , "Type of fruit from which bergamot comes" , "Citrus fruit; colour" , "stocking filler" , "Unrhymable word?" .)