Clear, as a chalkboard (5)
I believe the answer is:
erase
'clear as a chalkboard' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for erase that I've seen before include "Rub out, cancel" , "Remove all traces of" , "Destroy recording on audio or video tape" , "Clear" , "Obliterate" .)