Possible Clues:

• Just a shade cowardly, like 29 across
• Cowardly - kind of fever
• Just a shade craven to cry out like this
• Colour of cowardice, custard
• Behave just a shade 21 across with pain?
• This card is shown by soccer referee as a caution
• Colour - cowardly
• Colour of egg yolk and cowardice
• Small European bunting
• It's not even a shade brave to cry out like this