Obscenity from Siemens corporation backfired (4)
I believe the answer is:
smut
'obscenity' is the definition.
(I've seen this before)
'siemens corporation backfired' is the wordplay.
'siemens' becomes 'S' (synonyms).
'corporation' becomes 'tum' ('corporation' can humorously mean belly fat).
'backfired' says the letters should be written backwards.
'tum' reversed gives 'mut'.
's'+'mut'='SMUT'
'from' is the link.
(Other definitions for smut that I've seen before include "Soot flake or sexual innuendo" , "Soot flake; cereal disease" , "blue material" , "Piece of dirt or salacious talk" , "Dirty stuff" .)