Large building left in order (6)
I believe the answer is:
castle
'large building' is the definition.
'left in order' is the wordplay.
'left' becomes 'l' (common abbreviation).
'in' is an insertion indicator.
'order' becomes 'caste' (I've seen this in other clues).
'l' placed within 'caste' is 'CASTLE'.
(Other definitions for castle that I've seen before include "fortification" , "Chess piece and grand house" , "Rook, on chess board" , "Large building; rook" , "Move two pieces" .)