Really really disheartened as before (9)
I believe the answer is:
sincerely
'really' is the definition.
(I've seen this before)
'really disheartened as before' is the wordplay.
'disheartened' means to remove the middle letters (the middle or heart is removed).
'as' becomes 'since' (both can mean 'because').
'before' says to put letters next to each other.
'really' with its centre taken out is 'rely'.
'rely' after 'since' is 'SINCERELY'.
(Other definitions for sincerely that I've seen before include "In a genuine way" , "With genuine feeling" , "Genuinely, honestly" , "word often preceding a signature" , "Really" .)