Opens out black weaving machines (6)
I believe the answer is:
blooms
'opens out' is the definition.
(as in a flower opening up)
'black weaving machines' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'weaving machines' becomes 'looms' (machines for weaving fabric).
'b'+'looms'='BLOOMS'
(Other definitions for blooms that I've seen before include "Develops" , "Flowers" , "comes out" , "Flourishes" .)