Black — then hurry to get clean? (5)
I believe the answer is:
brush
'clean?' is the definition.
(I know that brush is a type of clean)
'black then hurry' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'then' means one lot of letters go next to another.
'hurry' becomes 'rush' (synonyms).
'b'+'rush'='BRUSH'
'to get' acts as a link.
(Other definitions for brush that I've seen before include "Sweeping implement" , "Undergrowth, fox tail" , "Tool for cleaning or painting" , "Slight touch; fox's tail" , "Cleaning implement" .)