To eat about six would be heavenly (6)
I believe the answer is:
divine
'heavenly' is the definition.
(similar in meaning)
'to eat about six' is the wordplay.
'to eat' becomes 'dine' (to dine is to eat a meal).
'about' indicates putting letters inside.
'six' becomes 'VI' (Roman numerals).
'dine' enclosing 'vi' is 'DIVINE'.
'would be' is the link.
(Other definitions for divine that I've seen before include "clergyman" , "Like a god; delightful" , "wonderful" , "Predict" , "Appertaining to God" .)