Weaving device (4)
I believe the answer is:
'weaving device' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for loom that I've seen before include "Rise up threateningly ahead" , "Weaving machine to appear indistinctly" , "Menace - weaving device" , "Machine for weaving yarn" , "Bulk large" .)