have an ace/a trick up your sleeve

have a trick up (one's) sleeve

To have a secret plan, idea, or advantage that can be utilized if and when it is required. A reference to cheating at a card game by hiding a favorable card up one's sleeve. I've got a few tricks up my sleeve if he decides to pursue legal action against me.
See also: have, sleeve, trick, up

have an ace up (one's) sleeve

To have a secret plan, idea, or advantage that can be utilized if and when it is required. A reference to cheating at a card game by hiding a favorable card up one's sleeve. I have an ace up my sleeve for this race—my stamina. The other runners don't stand a chance! I hear that the defense attorney has an ace up her sleeve—a new eye-witness.
See also: ace, have, sleeve, up
Farlex Dictionary of Idioms.

have an ace up your sleeve

have an effective resource or piece of information kept hidden until it is necessary to use it; have a secret advantage.
The ace is the highest playing card in its suit in many card games, so a cheating player might well hide one to use against an unwary opponent. A North American variant is an ace in the hole . The next two idioms are also based on this meaning of ace .
See also: ace, have, sleeve, up
Farlex Partner Idioms Dictionary

have an ˌace/a ˌtrick up your ˈsleeve

(British English) (American English have an ˌace in the ˈhole) (informal) have an idea or plan which you keep secret and can use if you need to (especially in order to gain an advantage over somebody): They think they’ve won the contract but we’ve still got a couple of aces up our sleeve.
See also: ace, have, sleeve, trick, up
Farlex Partner Idioms Dictionary
See also:
  • a card up (one's) sleeve
  • ace up (one's) sleeve
  • card up one's sleeve
  • have a card up (one's) sleeve
  • have a trick up (one's) sleeve
  • have an ace up (one's) sleeve
  • have something up your sleeve
  • have up sleeve
  • have/keep something up your sleeve
  • trick up (one's) sleeve