WP Job Manager Field Editor - strip all HTML from textarea field type for specific meta key

functions.php

<?php

add_filter( 'job_manager_get_posted_textarea_field', 'smyles_return_textarea_handler' );

function smyles_return_textarea_handler( $handler ){
    return 'smyles_get_textarea_handler';
}

function smyles_get_textarea_handler( $key, $field ){

    // This is default WP Job Manager handling/sanitization
    $value = isset( $_POST[ $key ] ) ? wp_kses_post( trim( stripslashes( $_POST[ $key ] ) ) ) : '';

    // In this example we target the `job_description` field (must be set to textarea in field config)
    if( $key === 'job_description' ){
        $value = wp_strip_all_tags( $value );
    }

    return $value;
}