Cube consumed orally (5)
I believe the answer is:
eight
'cube' is the definition.
(8 is a cube number)
'consumed orally' is the wordplay.
'consumed' becomes 'ate' (eating is a kind of consuming).
'orally' indicates a 'sounds like' (homophone) clue.
'ate' is a homophone of 'EIGHT'.
(Other definitions for eight that I've seen before include "No. of stones in cwt." , "power of two" , "Four twos" , "Number etched by a skater?" , "4 x 2" .)