Exercise spot that's unlawfully occupied (5)
I believe the answer is:
squat
'exercise' is the definition.
(I know that squat is a type of leg exercise)
'spot that's unlawfully occupied' is the wordplay.
I cannot quite see how this works, but
'occupied' could be 'at' (being occupied or busy at something) and 'at' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for squat that I've seen before include "Short, low" , "Stout" , "Short and fat" , "short but well-filled?" , "Illegally occupy property" .)