Cut of steak (4)
'cut of steak' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for rump that I've seen before include "Cut of meat from the rear" , "Inferior remains; cut of steak" , "Animal's hind quarters" , "Depleted legislators" , "Rear; buttocks" .)
(Other definitions for topside that I've seen before include "a cut above the others?" , "Deposit (anag) -- cut of meat" , "Outer cut of beef" , "Cut of beef from thigh" , "Towards ship's upper decks; part of cut of beef" .)