Go off on sabbath leaving clothes round building (7)
I believe the answer is:
rotunda
'round building' is the definition.
(architectural term)
'go off on sabbath leaving clothes' is the wordplay.
I cannot really see how this works, but
'go off' could be 'rot' (as in food going off) and 'rot' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for rotunda that I've seen before include "Circular building with a dome" , "Circular room or building" , "domed hall" , "Round domed building" , "Italian Pantheon, for instance" .)