Chicken or canary? (6)
I believe the answer is:
yellow
This clue is a triple definition!
'chicken' is the first definition.
(as in cowardly)
'or' is the second definition.
('or' is the heraldic name for gold or yellow)
'canary' is the third definition.
(type of yellow)
(Other definitions for yellow that I've seen before include "show sign of age" , "Colour of sunflowers and ripe lemons" , "Fearful - colour" , "Part of egg" , "'Caution' colour" .)