have up sleeve
have something up one's sleeveand have an ace up one's sleeve
Fig. to have a secret or surprise plan or solution (to a problem). (Alludes to cheating at cards by having a card hidden in one's sleeve.) I've got something up my sleeve, and it should solve all your problems. I'll tell you what it is after I'm elected. The manager has an ace up her sleeve. She'll surprise us with it later.
have something up your sleeve
to have a secret idea or plan If this trip doesn't work out I've still got a few ideas up my sleeve.