Schoolwork every prisoner should have (8)

I believe the answer is:

exercise

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'have' is the definition.
The answer and definition can be both related to bodily activities as well as being verbs in their base form.
Maybe there's a link between them I don't understand?

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for exercise that I've seen before include "problem" , "Train, work out" , "Task for pupil" , "worry" , "that every prisoner should have" .)

I've seen this clue in The Globe and Mail.

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