Gin diet so fantastic it helps with a breakdown (9)
I believe the answer is:
digestion
'it helps with a breakdown' is the definition.
The definition suggests a singular noun which matches the answer.
'gin diet so fantastic' is the wordplay.
'fantastic' indicates anagramming the letters (a fantastic or improbable ordering of the letters).
'gin'+'diet'+'so'='gindietso'
'gindietso' anagrammed gives 'DIGESTION'.
Can you help me to learn more?
(Other definitions for digestion that I've seen before include "process of breaking down" , "Process of assimilating food" , "Processing of food" , "mental assimilation" , "The absorbing of food" .)