New mode of building (4)
I believe the answer is:
dome
'building' is the definition.
(I've seen this before)
'new mode' is the wordplay.
'new' indicates anagramming the letters.
'mode' is an anagram of 'DOME'.
'of' acts as a link.
(Other definitions for dome that I've seen before include "Rounded vault of a roof" , "A stately building" , "Rounded roof with circular base" , "millennium feature" , "Curved roof" .)