Hard-working forward Griffiths - in good form this season - finished off a clever move on the stroke of half-time after a competitive first period in which we dominated the first 20 minutes before the Cherries played their way into the game.
A defensive error five minutes after the restart cost the hosts dearly, however, with Griffiths proving deadly as he helped himself to a second goal.
Paris Maghoma hit the bar and substitute Tashan Oakley-Boothe had an effort cleared off the line before substitute Clarke wrapped up a 3-0 win when goalkeeper Will Dennis parried Maghoma's shot into his path.