You used to be grand (4)
I believe the answer is:
thou
I believe this is a double definition.
'you' is the first definition.
(I've seen this in other clues)
'to be grand' is the second definition.
(thesaurus)
'used' acts as a link.
(Other definitions for thou that I've seen before include "Archaic pronoun" , "Second person in the Bible" , "You (archaic, but still used in prayers)" , "Prominent pronoun of the King James Bible; the modern-day 'you'" , "Biblical 'you'" .)