Visible horizon (7)
I believe the answer is:
skyline
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">visible horizon</span>' is the definition.<br/ ><span class="explanation-format__explanation">(synonyms)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(Other definitions for skyline that I've seen before include "Built-up horizon" , "Silhouette or outline of buildings" , "Horizon; like NY's (anag.)" , "Visible horizon" , "Outline of hills or buildings against firmament" .)