Towered (6)
I believe the answer is:
loomed
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">towered</span>' is the definition.<br/ ><span class="explanation-format__explanation">('loom' can be a synonym of 'tower')</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for loomed that I've seen before include "Soared threateningly ahead" , "came ominously close" , "Rose threateningly ahead" , "Came into view indistinctly, often threateningly" , "Appeared indistinctly, as in a mist" .)