Rotten time for coarse food (8)
I believe the answer is:
roughage
'coarse food' is the definition.
(I've seen this before)
'rotten time' is the wordplay.
'rotten' becomes 'rough' (I can't explain this - if you can you should believe this answer much more).
'time' becomes 'age' (an age is a period of time).
'rough'+'age'='ROUGHAGE'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for roughage that I've seen before include "Healthy fare" , "Indigestible material to stimulate intenstines" , "something that can make your passing more bearable" , "Essential food" , "Indigestible fibre" .)