Completed shelter - but it has no roof! (4)
I believe the answer is:
over
'completed' is the definition.
(synonyms)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for over that I've seen before include "Finished like cricket session" , "bowling unit" , "remaining" , "See 12" , "Finished-up -left" .)