keep (something) up (one's) sleeve

keep (something) up (one's) sleeve

To keep something, such as a plan or advantage, in secret so it 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. What the other runners don't know is that I've kept an ace up my sleeve for this race—my stamina. I've been keeping a few tricks up my sleeve if he decides to pursue legal action against me.
See also: keep, sleeve, up
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.

have/keep something up your ˈsleeve

(informal) have a good idea, plan or piece of information which you are not telling anyone about now, but which you intend to use later: John was smiling to himself all through the meeting; I’m sure he’s got something up his sleeve.
See also: have, keep, sleeve, something, up
Farlex Partner Idioms Dictionary © Farlex 2017
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