Coat-tails are the two long pieces at the back of a tailcoat .
PHRASE
沾…的光;靠…的提携
If you do something on the coat-tails of someone else, you are able to do it because of the other person's success, and not because of your own efforts.
例句
They accused him of riding on the coat-tails of the president.他们指责他是沾了总统的光。