Sailing boat south with wind (5)
I believe the answer is:
sloop
'sailing boat' is the definition.
(type of sailing boat)
'south with wind' is the wordplay.
'south' becomes 'S' (synonyms).
'with' means one lot of letters go next to another.
'wind' becomes 'loop' (looping is a kind of winding).
's'+'loop'='SLOOP'
(Other definitions for sloop that I've seen before include "something that's rigged" , "One-masted sailing boat" , "Single-masted sailing boat" , "Vessel with a single mast" , "craft" .)