Can lose oar at sea (7)
I believe the answer is:
aerosol
'can' is the definition.
(I've seen this before)
'lose oar at sea' is the wordplay.
'at sea' is an anagram indicator.
'lose'+'oar'='loseoar'
'loseoar' is an anagram of 'AEROSOL'.
(Other definitions for aerosol that I've seen before include "What makes mist" , "O so real (anag.)" , "source of graffiti?" , "Air-spray" , "Sprayer" .)