Spray that's dropped picked up (4)
I believe the answer is:
mist
'spray' is the definition.
(misting is a kind of spraying)
'dropped picked up' is the wordplay.
'dropped' becomes 'missed' ('miss' can be a synonym of 'drop').
'picked up' indicates a 'sounds like' (homophone) clue.
'missed' sounds like 'MIST'.
'that's' acts as a link.
(Other definitions for mist that I've seen before include "Mizzle; light rain" , "Fine spray" , "Fret" , "Obscure" , "Slight fog" .)