WordPress at a glance
function is not described

wp_clean_themes_cache() WP 3.5.0

Clears the cache held by get_theme_roots() and WP_Theme.

No Hooks.

Return

Nothing (null).

Usage

wp_clean_themes_cache( $clear_update_cache );
$clear_update_cache(true/false)
Whether to clear the Theme updates cache
Default: true

Code of wp clean themes cache: wp-includes/theme.php WP 5.2.2

<?php
function wp_clean_themes_cache( $clear_update_cache = true ) {
	if ( $clear_update_cache ) {
		delete_site_transient( 'update_themes' );
	}
	search_theme_directories( true );
	foreach ( wp_get_themes( array( 'errors' => null ) ) as $theme ) {
		$theme->cache_delete();
	}
}