CIA keeping dry put up in top room (5)
I believe the answer is:
attic
'top room' is the definition.
(I've seen this in another clue)
'cia keeping dry put up' is the wordplay.
'keeping' indicates putting letters inside (some letters kept inside).
'dry' becomes 'tt' (abbreviation for teetotal).
'put up' says the letters should be written in reverse.
'cia' enclosing 'tt' is 'citta'.
'citta' backwards is 'ATTIC'.
'in' is the link.
(Other definitions for attic that I've seen before include "Greek - upper room" , "Loft room" , "of Greek region" , "Dusty room" , "Ancient Greek; loft" .)