One with cold is after a dry room (5)
I believe the answer is:
attic
'room' is the definition.
(I've seen this before)
'one with cold is after a dry' is the wordplay.
'one' becomes 'i' (Roman numeral**).
'with' says to put letters next to each other.
'cold' becomes 'c' (eg on taps).
'is after' is a charade indicator (letters next to each other).
'dry' becomes 'tt' (abbreviation for teetotal).
'i'+'c' is 'ic'.
'a'+'tt'='att'
'ic' after 'att' is 'ATTIC'.
(Other definitions for attic that I've seen before include "Dusty room" , "cockloft" , "room with lots of junk?" , "Tacit (anag.)" , "of Greek region" .)