have something up your sleeve
idiomPart ofsleeve
have something up your sleeve — idiom
1. to have a secret plan, idea, or piece of information that you keep hidden so tha
1.idiom
Definition
to have a secret plan, idea, or piece of information that you keep hidden so that you can use it later to gain an advantage.
Example
The other team seemed confident, but our coach had a surprise strategy up his sleeve.
I do not know what Amira has up her sleeve, but she seems very sure the plan will work.