Senior official of the House of Lords (5,3)
I believe the answer is:
black rod
'senior official of the house of lords' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for black rod that I've seen before include "Government official" , "Parliamentary official" , "Official usher" , "Gentleman Usher of the Palace of Westminster" , "Officer of the House of Lords" .)