Colourful cardinal (3)
I believe the answer is:
red
This clue is a double definition.
'colourful' is the first definition.
(similar in meaning)
'cardinal' is the second definition.
(I've seen this in other clues)
(Other definitions for red that I've seen before include "Blushing" , "Glowing" , "'If you see it, perhaps you're angry (3)'" , "Colour of 1 across" , "Scarlet or vermilion" .)