River in Siberia reporter’s identified as foul (7)
I believe the answer is:
obscene
'foul' is the definition.
(thesaurus)
'river in siberia reporter's identified' is the wordplay.
'river in siberia' becomes 'Ob' (Ob is a Russian river).
'reporter's' shows a homophone (sound like) (report can mean to speak something aloud).
'identified' becomes 'seen' (identify can mean to recognise or see).
'seen' sounds like 'scene'.
'ob'+'scene'='OBSCENE'
'as' acts as a link.
(Other definitions for obscene that I've seen before include "Offensive - indecent" , "not decent" , "offending sensibilities?" , "One's CBE (anag)" , "Dirty" .)