Ventilator black, inferior (6)
I believe the answer is:
blower
'ventilator' is the definition.
(thesaurus)
'black inferior' is the wordplay.
'black' becomes 'b' (abbreviation as in pencil classifications).
'inferior' becomes 'lower' (similar in meaning).
'b'+'lower'='BLOWER'
(Other definitions for blower that I've seen before include "Fan; telephone (colloq.)" , "Fan - phone" , "Fan - telephone (slang)" , "Speaking-tube" , "Telephone (informal)" .)