High-rise building (5,5)
I believe the answer is:
tower block
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">high-rise 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 tower block that I've seen before include "Tall residential or office building" , "high-rise building" , "Tall building of offices, flats" , "Skyscraper" , "big build-up?" .)