a man wearing black rides a unicycle.
A man is practicing riding a unicycle for his circus audition.
He can't be said to be preparing for a circus audition; he could just be riding for fun.
exists x1 x2.(a_topic(x1) & all x3.(n_unicycle(x3) -> exists e1 s1 x4.(Theme(e1,x4) & Actor(e1,x2) & v_wear(e1) & for(x4,x3) & n_ride(x4) & a_black(s1) & Theme(s1,x4))) & (x1 = x2) & n_man(x1))
exists e1 p1 x1 x3 x4.(exists e2 x2.(for(e2,x3) & Theme(e2,x2) & Actor(e2,x1) & v_ride(e2) & n_unicycle(x2)) & n_audition(x3) & of(x3,x4) & n_circus(x4) & of(x3,x1) & n_male(x1) & Topic(e1,p1) & Actor(e1,x1) & v_practice(e1) & n_man(x1))