Shelter? Shelter has no roof! (6)
I believe the answer is:
arbour
'shelter?' 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?
'shelter has no roof' is the wordplay.
'shelter' becomes 'harbour' (harbouring is a kind of sheltering).
'has no roof' means to remove the first letter.
'harbour' with its first letter taken off is 'ARBOUR'.
Can you help me to learn more?
(Other definitions for arbour that I've seen before include "Shady alcove; bower" , "Shady garden alcove" , "Retreat" , "Secluded garden alcove" , "Sheltered leafy glade" .)