Use up nourishing food, apart from nut, being greedy (8)
I believe the answer is:
esurient
'greedy' is the definition.
(synonyms)
'use up nourishing food apart from nut' is the wordplay.
'up' is a reversal indicator (in down clue: letters go upwards).
'nourishing food' becomes 'nutrient' (food with good nutritional value).
'apart from' is a deletion indicator.
'use' reversed gives 'esu'.
'nutrient' with 'nut' taken out is 'rient'.
'esu'+'rient'='ESURIENT'
'being' is the link.
(Other definitions for esurient that I've seen before include "could eat a horse" , "Rapacious" , "Greedy; ensure it (anag.)" , "Hungry, greedy" , "Hungry; retinues (anag.)" .)