<?php // don't include this line in your functions.php, since it already starts with it.

function _remove_team_members_si_toggl_import_entries( $time_entries = array() ) {
	foreach ( $time_entries as $key => $time_entry ) {
		if ( isset( $time_entry->tags ) ) { // it's likely not
			$tag_array = json_decode( $time_entry->tags );
			if ( ! in_array( 'filterTAG', $tag_array ) ) { // filterTAG is the tag you only want to import
				unset( $time_entries[$key] ); // remove
			}
		}
	}
	return $time_entries;
}
add_filter( 'si_toggl_import_entries', '_remove_team_members_si_toggl_import_entries' );