Clean, as one quietly points out (4)
I believe the answer is:
wipe
'clean' is the definition.
(I've seen this in another clue)
'one quietly points out' is the wordplay.
'one' becomes 'i' (Roman numeral).
'quietly' becomes 'p' (p for piano and quiet).
'points' becomes 'we' ().
'out' is an insertion indicator.
'i'+'p'='ip'
'ip' put inside 'we' is 'WIPE'.
'as' acts as a link.
(Other definitions for wipe that I've seen before include "Cancel (tape)" , "Swab" , "use cloth" , "strike" , "Rub lightly to remove dust, etc" .)