Archive page excerpt pulls iframe code text

Theme is calling get_the_excerpt function in Archive page and does not strip the iframe code text. Please see cafoundationfund.org/projects

What do I need to do to add a function that allows the excerpt text to be trimmed properly? Perhaps adding a snippet directly to the child-theme functions.php?

The get_the_excerpt output which trims (and strips tags from) the excerpt, callback wp_trim_excerpt (inside of this callback the function wp_trim_words)` code might work best in the child-theme functions.php

Please provide the PHP snippet code to fix this problem.

By the way, the blog page seems to be doing ok: cafoundationfund.org/news