Sign of something extra, or amount of gold, announced as incentive (6)
I believe the answer is:
carrot
'incentive' is the definition.
(as in a carrot and stick)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for carrot that I've seen before include "Pointed vegetable" , "Orange vegetable" , "Orangey vegetable" , "The vegetable for persuasion" , "Red vegetable used as inducement" .)