Very disappointed (11)
'very disappointed' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for sick as a parrot that I've seen before include "Really gutted" , "Severely disappointed" , "badly gutted" , "Extremely disappointed (colloq.)" , "Awfully disappointed" .)
(Other definitions for crestfallen that I've seen before include "Dejected after blow to pride" , "Downcast" , "in a sorry condition" , "Feeling a blow to one's pride" , "Sadly disappointed" .)