Imposing building (7)
I believe the answer is:
edifice
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">imposing building</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this before)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for edifice that I've seen before include "impressive pile!" , "Permanent building" , "Impressive building" , "Large structure" , "erection" .)