Hungry Hippo, empty and d-depressed? (6)
I believe the answer is:
hollow
'hungry' is the definition.
(thesaurus)
'hippo empty and d-depressed?' is the wordplay.
'empty' suggests removing the centre.
'and' says to put letters next to each other.
'd-depressed?' becomes 'llow' ('low' said with a stutter like 'depressed?' was; 'low' can be similar in meaning to 'depressed').
'hippo' with its centre removed is 'ho'.
'ho'+'llow'='HOLLOW'
(Other definitions for hollow that I've seen before include "Empty - insincere" , "Empty space within" , "Concave; empty inside" , "Empty - hole" , "Empty, not solid" .)