A lord, we hear, is to show up (6)
I believe the answer is:
appear
'is to show up' is the definition.
(both can mean to arrive)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for appear that I've seen before include "Seem - come into view" , "Seem or materialise" , "Perform" , "Come into sight, materialise" , "hove in sight" .)