Dry in southeast and cold (3)
I believe the answer is:
sec
'dry' is the definition.
('dry' in French - used for wine)
'southeast and cold' is the wordplay.
'southeast' becomes 'SE' (synonyms).
'and' says to put letters next to each other.
'cold' becomes 'C' (eg on taps).
'se'+'c'='SEC'
'in' acts as a link.
(Other definitions for sec that I've seen before include "21 down, as wine" , "Moderately dry, champagne say" , "Dry wine perhaps" , "sort of function" , "'Dry, as wine (3)'" .)