Room accommodating squatters? (3)
I believe the answer is:
gym
'room accommodating squatters?' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
This is all the clue.
Can you help me to learn more?
(Other definitions for gym that I've seen before include "Place to work out" , "Training room" , "Area for physical exercise in short" , "Physical training facility, in short" , "Physical education" .)