Disturbed dust on a floor (7)
I believe the answer is:
astound
'floor' is the definition.
(I've seen this before)
'disturbed dust on a' is the wordplay.
'disturbed' is an anagram indicator (the order of letters is disturbed).
'dust'+'on'+'a'='dustona'
'dustona' is an anagram of 'ASTOUND'.
(Other definitions for astound that I've seen before include "Startle" , "Stupefy" , "Bewilder" , "Bowl over" , "Flabbergast" .)