hold (something) in reserve
To save something or set it aside for future use. Most people would be shocked if they knew how much money the government holds in reserve. I'm holding those snacks in reserve for the road trip.
hold someone or something in reserve and keep someone or something in reserve
Fig. to hold back someone or something for future needs. I am holding the frozen desserts in reserve, in case we run out of cake. We are holding Sharon in reserve. Keep a few good players in reserve.