Setting a /clear @a command on a setblock clock will result in the inventory of the player being cleared, but then all new items put into their inventory remain visible until interacted with, whereupon they disappear.

Test:
1. Make a setblock clock: "/setblock ~ ~1 ~ air" and "/setblock ~ ~-1 ~ redstone_block"

2. Put a command block with /clear @a on the clock.

3. Place new items into your inventory

4. Place down the block/splash the potion/etc. (ie right click with the item)

5. Item disappears and any placed blocks using that item appears for a split second and disappears.