Cessna 210 pilot reported entering into a stall during approach due to attempting to climb using reduced power setting. Pilot added power and regained aircraft control.

Narrative

I was flying my aircraft at end of 8 hour flight from ZZZ1 to ZZZ with refuel stop at ZZZ2 and was being vectored for the ILS at ZZZ. I had ATIS and was being vectored downwind and anticipating a base turn and descent followed by turn to intercept the ILS. I was still on autopilot and power was back up to 60%. My altitude was 5000 FT so I anticipated a descent to 4000 FT to intercept the ILS outside ZZZZZ. I was on ZZZ control frequency for this approach. Suddenly the ZZZ Controller told me to climb immediately. I pulled hard to zoom click instantly to 5500 FT but I was on low power settings and after reaching 5300 FT the AOA showed impending stall and the airspeed was falling rapidly and the nose of the plane started to fall. I pushed MP (Manifold Pressure/Throttle) in and turned autopilot off and focused on regaining control of the airplane; RPM/FF (Fuel Flow) still pulled back. I saw traffic pass off my left so I regained control of the plane at about 5000 FT. I reconfigured for more power with full fuel and RPM 2500. The ZZZ Controller was furious that I failed to immediately climb and maintain 5500 FT. He then turned me on base leg and to intercept the ILS and I landed uneventfully. If I had more notice of an aircraft climbing directly toward me; I could have gone to climb power and easily climbed and maintained 5500 FT.