Machine for weaving (4)
I believe the answer is:
loom
'machine for weaving' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for loom that I've seen before include "'Appear as a vague form, perhaps threatening (4)'" , "Weaving - apparatus - overhang" , "Apparatus for weaving cloth" , "Rise up threateningly ahead" , "Appear large and indistinct, to weave?" .)