if you have sth. up your sleeves, you have some ready but secret gimmicks, tricks or means to be used if you roll up your sleeves, you are getting ready to fight or toil at something difficult

The correct term can be one of the following: have something up one's sleeve/have an ace up one's sleeve/have a trick up one's sleeve. It means to have a secret/surprise plan or solution to a problem. How to use it: I've got a trick up my sleeve that will solve all your problems.