Sustenance during alimentary abstinence? (4,4)
I believe the answer is:
fast food
'sustenance' is the definition.
(thesaurus)
'during alimentary abstinence?' is the wordplay.
I cannot quite understand how this works, but
'abstinence?' could be 'fast' (fast is a kind of abstinence) and 'fast' is found within the answer.
The remaining letters 'food' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for fast food that I've seen before include "Fish and chips, burgers, etc" , "Burgers or kebabs (but not snails!)" .)