Thanks everyone! What's a satrap? I'd got the trap bit (part backwards) but couldn't get the two prior letters.
Have never heard of a neatherd either!
Strill can't get 22a
20d Agreement to omit introduction at start of second book 4 _ _ _ S
21d Shock when bird is heard 4 _ _ _ N STUN?
A satrap was a governor of a province in ancient Persia
Neat is an old word for cattle
20d Acts (agreement is pact, leave off the P and add start of second)