Jar reported to be large (5)
I believe the answer is:
great
'be large' is the definition.
('great' can be a synonym of 'large')
'jar reported' is the wordplay.
'jar' becomes 'grate' (make unpleasant sound).
'reported' shows a homophone (sound like).
'grate' is a homophone of 'GREAT'.
'to' is the link.
(Other definitions for great that I've seen before include "Large; fine" , "Marvellous; big" , "Very large in size, quantity, etc." , "Enormous" , "Of major significance - very good" .)