Wash thoroughly (5)
(Other definitions for clean that I've seen before include "Wash" , "attentive to personal hygiene" , "Second part of 18" , "Free from contamination - entirely" , "Not dirty" .)
'wash thoroughly' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for scrub that I've seen before include "Take out - clean" , "plants" , "Cancel (colloq)" , "Wash the stunted shrub?" , "Clean with hard brush and soapy water" .)
(Other definitions for cleanse that I've seen before include "purify from sin" , "Make spotless" , "Make thoroughly clean" , "clear of muck" , "Wash" .)