Part of diet that keeps you ethically regular (5,5)
I believe the answer is:
moral fibre
'diet that keeps you ethically regular' is the definition.
I don't know anything about this answer so I cannot judge whether this works.
'part of' is the wordplay.
I cannot really understand how this works, but
'part' could be 're' (re is a kind of part) and 're' is located in the answer.
'of' could be 'o' and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for moral fibre that I've seen before include "Strength of character" , "guts - with 24a" .)