Steven P. McNicoll wrote:
While "cancel previous approach clearance" is probably a good idea for
clarity, it is not required.

What instructions/clearances can ATC issue to a flight after issuing
an approach clearance which wouldn't automatically cancel the approach
clearance?

Some instructions obviously don't: "Contact tower 123.45", for
example. I would think that any instruction which included an
altitude restriction, or a heading/route to fly, would. Any other
cases which I haven't thought of?