Harry to make noble case for empty sentiment (6)
I believe the answer is:
pester
'harry' is the definition.
(I've seen this in another clue)
'noble case for empty sentiment' is the wordplay.
'noble' becomes 'peer' (peer is a kind of noble).
'case for' is an insertion indicator.
'empty' means to remove the middle letters.
'sentiment' with its middle taken out is 'st'.
'peer' going around 'st' is 'PESTER'.
'to make' is the link.
(Other definitions for pester that I've seen before include "Harass" , "Annoy with frequent requests" , "Annoy with frequent questions" , "Annoy persistently" , "Be a nuisance, annoy with requests" .)