Exercise? Right kind should be easy to follow (4-8)
I believe the answer is:
user-friendly
'easy to follow' is the definition.
I can't tell whether this definition defines the answer.
'exercise? right kind' is the wordplay.
'exercise? right' becomes 'user' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'kind' becomes 'friendly' ('friendly' can be a synonym of 'kind').
'user'+'friendly'='USER-FRIENDLY'
'should be' is the link.
Can you help me to learn more?
(Other definitions for user-friendly that I've seen before include "Easy to understand or manipulate" , "Easy to operate" , "Easily picked up" .)