Not sure I understand your goal? Are you trying to make sure they are killed sooner?

You didn't post your location or zone but yes, pansies will die out this time year anywhere it is getting very hot and humid. The entire plant, including the roots, will die. You don't need to do any clipping at all. They will die on their own.

Afraid that you need to yank all of those pansies if you live in a warmer climate. In the south, you need to plan early to replace the pansies before you really want to, or the supplies of nice summer annuals will be gone.

Hi everyone, are there any varieties of pansies that tolerate heat and tropical conditions ?

No. There are some that are slightly more heat tolerant than others, but they all have serious problems with heat. In warm climates, they can be grown in the winter time, as long as there is a winter.