Close things seen by Yankee (6)
I believe the answer is:
stuffy
'close' is the definition.
(both can mean uncomfortably warm)
'things seen by yankee' is the wordplay.
'things' becomes 'stuff' (I've seen this before).
'seen by' is a charade indicator (letters next to each other).
'yankee' becomes 'Y' (phonetic alphabet: alpha, bravo, charlie etc.).
'stuff'+'y'='STUFFY'
(Other definitions for stuffy that I've seen before include "Airless - pompous" , "Priggish" , "Airless; unadventurous" , "Old-fashioned" , "Strait-laced -- lacking fresh air" .)