Can an issued landing clearance be replaced with "continue approach"? Since the US handles the landing clearance differently, this is limited to Europe (EASA-land).
From Eurocontrol:

Continue Approach
If the runway is obstructed when the aircraft reports ‘final’, but it is expected to be available in good time for the aircraft to make a safe landing, the controller will delay landing clearance by issuing an instruction to ‘continue approach’. The controller may explain why the landing clearance has been delayed. An instruction to ‘continue’ is NOT a clearance to land.

I understand it's also used for sequencing, e.g., continue approach number 2, number 3, etc.

Here's the scenario:
STACK 1 has been cleared to land, and is 8 NM out. STACK 88 was holding short and was requesting sometime to verify something, but now they are ready.

STACK 88: Tower, Stack 88 is now ready for departure.

Tower: Stack 88, traffic 8 mile final, are you ready for immediate departure?

STACK 88: Affirm, Stack 88 is ready.

Tower: Stack 88, cleared for immediate takeoff, no delay.

STACK 88: Cleared for immediate takeoff.

Tower: Stack 1, cancel landing clearance, continue approach number 1, traffic departing, minimum approach speed.

STACK 1: Roger, continue approach, minimum approach speed.

Is the above exchange correct? In terms of both procedures and phraseology, i.e., can a landing clearance be cancelled for reasons other than a go-around instruction?
The example is correct, except that the landing clearance for stack 1 must be cancelled before the takeoff clearance is given to stack 88. The logic is that only one aircraft can ever be cleared to land on or take off from a given runway at any one time. So in your example, you just have to swap the order of instructions 3 and 4.

Stack 1 cancel landing clearance, continue approach
Continue approach, Stack 1
Stack 88 runway 12 cleared for takeoff
Runway 12 cleared for takeoff, Stack 88
...
Stack 1 runway 12 cleared to land