Boat made by company in the southwest (4)
I believe the answer is:
scow
'boat' is the definition.
(I know that scow is a type of boat)
'company in the southwest' is the wordplay.
'company' becomes 'co' (abbreviation).
'in' indicates putting letters inside.
'the southwest' becomes 'SW' ('SW' can be a synonym of 'southwest').
'co' placed inside 'sw' is 'SCOW'.
'made by' acts as a link.
(Other definitions for scow that I've seen before include "Maybe lighter" , "Unpowered freight barge" , "Flat-bottomed boat for cows" , "Vessel" , "Wide-beamed dinghy" .)