Area of a new door (4)
I believe the answer is:
rood
'area' is the definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'a new door' is the wordplay.
'a new' indicates an anagram.
'door' with letters rearranged gives 'ROOD'.
'of' acts as a link.
Can you help me to learn more?
(Other definitions for rood that I've seen before include "Old land measure of quarter of an acre" , "Cross, crucifix" , "Area equal to 40 square rods" , "Pole, perch or crucifix" , "old piece of land" .)