a person in a position to use influence on your behalf
RELATED IDIOMS :
a fair-weather friend
someone who cannot be relied on in a crisis
1998 - Spectator - The Americans gave up supplying gold on demand to other countries' central banks at £35 an ounce when their fair-weather friends from London threatened to turn up and clean them out.
a credit card
This phrase comes from the advertising slogan…. Access your flexible friend.
friends in high places
people in senior positions who are able and willing to use their influence on your behalf