Main command
/setblock ~0 ~0 ~0 minecraft:redstone_block 0 destroy

Command to get a Command Block
/give @a 137

Command that makes the clock not spam block drops
/gamerule doTileDrops false

Command that doesn't spam the chat
/gamerule commandBlockOutput false

If you want a way to turn it on and off all you have to do, is place a lever on the command block. When the lever is on, the redstone clock is off, if the lever is off, then the clock is on

Ok so now you replace one of the Zeros in the setblock command with a 1 or -1, and then you place a redstone block beside the command block, this will tell you where to place it, if you need further help look in the video above

Materials:
1 Command block
2 Redsonte blocks
1 lever (optional)
Cya guys next time!