Colour of old cooker? (6)
I believe the answer is:
orange
'colour' is the definition.
(orange is a kind of colour)
'old cooker?' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'cooker?' becomes 'range' (I've seen this in other clues).
'o'+'range'='ORANGE'
'of' acts as a link.
(Other definitions for orange that I've seen before include "African flower" , "Colour between red and yellow" , "Unrhymable word?" , "Order of the North" , "Dutch royal house" .)