Get rid of a black sheen that phosphorus leaves (7)
I believe the answer is:
abolish
'get rid of' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for abolish that I've seen before include "Put an end to (something)" , "Put an end to, cancel" , "Put an end to (custom)" , "Annul - expunge" , "ditch" .)