Wash black articles (5)
I believe the answer is:
bathe
'wash' is the definition.
(I've seen this before)
'black articles' is the wordplay.
'black' becomes 'b' (abbreviation as in pencil classifications).
'articles' becomes 'a the' ('a' and 'the', indefinite and definite articles).
'b'+'athe'='BATHE'
(Other definitions for bathe that I've seen before include "Wash, soak" , "bit of swimming" , "go into rollers?" , "Immerse in liquid for wash" , "Wash in water" .)