Devise Your First Gym Activity In Safety Enclosure

[Samizme]

I think that this must be ‘playpen’ but can you explain why? Thanks Sam

[Neveracrossword]

Plan, devise, Y, your first (first letter of You) and PE, gym activity.

[bobbinwales]

Y for your
Pe for gym
In pLAN

[Neveracrossword]

...so Pla Y PE n.