Try and try to produce supportive comment (4,4)
I believe the answer is:
hear hear
'supportive comment' is the definition.
(comment used to show agreement)
'try and try' is the wordplay.
'try' becomes 'hear' (as in to try someone in court or hear their case).
'and' is a charade indicator (letters next to each other).
'try' becomes 'hear' (as in to try someone in court or hear their case).
'hear'+'hear'='HEAR HEAR'
'to produce' is the link.
(Other definitions for hear hear that I've seen before include "Listen, listen - that's applause!" , "Words of agreement" , "I quite agree!" , "I thoroughly agree!" , "Expression of agreement with something said" .)