Samsung Galaxy Ace 3 have own recovery from firmware, so whenever you try to install clockworkmode will always back to stock recovery when reboot your device.
How to install cwm permanent on galaxy ace 3? to make cwm permanent you need to delete stock recovery from file system, so you need to root your device first. See here How To Root Samsung Galaxy Ace 3.
Then if you done with the root, follow this step.
1. go to your file system/ root system using root explorer.
2.find this file and delete/rename it
3. You Done, finally try to flash the CWM again.