Cub: it is desperate for something to eat (7)
I believe the answer is:
biscuit
'something to eat' is the definition.
(biscuit is a kind of food)
'cub it is desperate' is the wordplay.
'desperate' is an anagram indicator.
'cub'+'it'+'is'='cubitis'
'cubitis' anagrammed gives 'BISCUIT'.
'for' is the link.
(Other definitions for biscuit that I've seen before include "Unglazed pottery" , "Small crisp cake" , "Eg, custard cream" , "Edible" , "Cookie - cracker" .)