Fix radius on out-and-out circular construction (7)
I believe the answer is:
rotunda
'circular construction' is the definition.
(I've seen this before)
'fix radius on out-and-out' is the wordplay.
I cannot quite see how this works, but
'radius' could be 'r' (abbreviation in geometry) and 'r' is found in the answer.
an anagram of 'out' is 'otu' which is within the answer.
an anagram of 'and' is 'nda' which is present in the answer.
No letters remain.
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 "Do a turn (anag) -- circular domed building" , "Round domed building" , "Circular building with a dome" , "circular construction" , "Circular room or building" .)