TOR. The figure above the line in a fraction. The one below is the denominator. 17 BUTTERFLY - B(owled) + UTTERLY around F(requency). Here's a skipper . 18 PASTORAL - PAST + ORAL. 21 LETHAL - LATEL(y) rev. around H(earts). 22 HOKUM - HUM around OK. 24 SHIRK - SH +