I remember seeing a coach or some advanced player toying around with the double action clear shots. I even fell for it as I never seen in action before.
I call it the hold and punch.
Gollum covered it briefly here in badminton bible. In hindsight, I would have identify it as what it is, but I rarely seen it in action.
As covered by Lee Jae Bok, there are three types of clear, 1) defensive clear 2) offensive clear 3) punch clear. Ref it here.
This is usually starts with a overhead shot side-way stand.
The person pretends to drop, even doing a jump to fake the shot.
This delaying (or Hold) gives the opponent the impression that the incoming shot will be a slice or drop.
The punch is launch when the player sees the opponent just before he/she began the weight shifting/split step.
Instead, the player never even make contact in the air. The player let the shuttle drop a little and hit it when the player's feet touched the ground.
When the player landed, he/she hit a clear by just tapping with the wrist (just like a goalkeeper punching the soccer ball). Hence a punch clear.
Here is one famous example, but clearly Lee Chong Wei was caught expecting a dropshot or smash by Lin Dan. Instead Lin Dan fake the drop/smash into a punch clear.
This is provided, the opponent hits a weak/weaker clear and you reach the shuttle early. The double action punch clear has the effect of the opponent stranded if he is caught just returning to base position. (a movement pressure tactic).
The hold and punch can even be applied on a backhand clear.
I remember Boonsak Ponsana executing a very strange shot that I have never seen before. It has the effect of fooling your eye via a backhand dropshot hold into a backhand clear.
However, if the hold and punch is predicted, the opponent can quickly jump up and cut it or even smash it if he can jumpback to get behind the shuttle.
[aka the block jump or China jump, (jumping footwork to the forehand corner)]
Use the hold and punch with caution against better players as any double action shots are just lifting or giving the opportunity for the opponent to attack. In doubles, this is somewhat suicidal as lifting the shuttle gives the initiative away.