Loomed up (5)
I believe the answer is:
arose
'loomed up' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for arose that I've seen before include "''. ... by any other name would smell as sweet'' (Romeo and Juliet)" , "appeared" , "Became apparent" , "Got out of bed" , "stemmed" .)