Towered (6)
I believe the answer is:
loomed
'towered' is the definition.
('loom' can be a synonym of 'tower')
This is all the clue.
(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" .)