Exercise is able to produce food (5)
I believe the answer is:
pecan
'produce food' is the definition.
The answer and definition can be both things that one consumes for nourishment as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'exercise is able' is the wordplay.
'exercise' becomes 'pe' (Physical Education).
'is able' becomes 'can' (if you can do something, you are able to do it).
'pe'+'can'='PECAN'
'to' is the link.
Can you help me to learn more?
(Other definitions for pecan that I've seen before include "nut-tree" , "Nut of American hickory tree" , "Edible nut like a smooth walnut" , "Type of nut" , "of nuts" .)