Sounds dejected, hearing of greatness (5)
I believe the answer is:
sighs
'sounds dejected' is the definition.
(to sigh is to sound dejected or tired)
'hearing of greatness' is the wordplay.
'hearing of' indicates a 'sounds like' (homophone) clue.
'greatness' becomes 'size'.
'size' is a homophone of 'SIGHS'.
(Other definitions for sighs that I've seen before include "Exhales sadly" , "Yearns" , "Bridge of - - (Venice)" , "Sounds of weariness" , "Sounds despondent" .)