Drops everything in empty factories (5)
I believe the answer is:
falls
'drops' is the definition.
('fall' can be a synonym of 'drop')
'everything in empty factories' is the wordplay.
'everything' becomes 'all' (I've seen this before).
'in' is an insertion indicator.
'empty' means to remove the middle letters.
'factories' with its middle removed is 'fs'.
'all' placed within 'fs' is 'FALLS'.
(Other definitions for falls that I've seen before include "North Country force" , "Victoria or Niagara, for example" , "Drops" , "Cascade" , "See 6 Down" .)