This is more of a guess than fact!
But if you look at the Genesis album cover from which the saying is taken:
http://phil_collins_fr.site.voila.fr...ms/08trick.jpg
you will see a scene including the devil who is know for both his 'tricks' and 'forked tail' in popular folklore. So I am guessing that it may mean 'The devils works' or 'devils tricky deeds'.
In other words "A trick (crafty deed) of the tail (devil)"
Purely guesswork!