After a goalless first half, Stuart Armstrong, Leigh Griffiths and Tony Watt got on the scoresheet after the break to secure three vital points. McLean came on for the last five minutes or so to make his competitive debut for the under-21s even though it was his first cap.
The Scots will secure a place in the play-offs for next year's European Championships if they win in Austria next week.
Follow Mirren Mad on Facebook at http://www.facebook.com/mirrenmad
Follow Mirren Mad on Twitter @mirren_mad or http://www.twitter.com/mirren_mad