Black Country is boring (5)
I believe the answer is:
bland
'boring' is the definition.
(I've seen this before)
'black country' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'country' becomes 'land' (synonyms).
'b'+'land'='BLAND'
'is' acts as a link.
(Other definitions for bland that I've seen before include "Mild and insipid" , "Dull - tasteless" , "Boringly characterless" , "Mild; dull" , "Unruffled but unstimulating" .)