Time wore away building (5)
I believe the answer is:
tower
'building' is the definition.
(I know that tower is a type of building)
'time wore away' is the wordplay.
'time' becomes 't' (abbreviation).
'away' indicates anagramming the letters (letters move away from their original places).
'wore' is an anagram of 'ower'.
't'+'ower'='TOWER'
(Other definitions for tower that I've seen before include "Tall column" , "Wrote (anag.)" , "tractor, perhaps" , "Steeple" , "famous prison" .)