Valuable casino cards (4)

I believe the answer is:

aces

(Other definitions for aces that I've seen before include "holes in one" , "wartime pilots?" , "Unreturnable services" , "Ones or elevens in cards" , "Two will make deuce" .)

I've seen this clue in The Washington Post.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.