add_filter( 'the_content', 'bimber_custom_find_yt', 10, 1 );

function bimber_custom_find_yt( $content ) {
	$findclip = 'youtube.com';
	$find = stripos($content, $findclip);
    if ( is_single() ){

        if ( $find !== false ){
				echo '<style>#content .entry-featured-media{display:none !important;}</style>';
			}
	};
    return $content;
}