Wipe clean (5)
'wipe clean' 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 "Destroy recording on audio or video tape" , "Clear" , "Efface" , "Blank out" , "Rub out, expunge" .)
(Other definitions for mop up that I've seen before include "Complete final stage (of a task)" , "Swab" , "Deal with spillage or defeated enemy" , "Finish a task, clear away remnants" , "Finish off a task, clean away remnants" .)