Close — prudish (6)
I believe the answer is:
stuffy
This clue is a double definition.
'close' is the first definition.
(both can mean uncomfortably warm)
'prudish' is the second definition.
(thesaurus)
(Other definitions for stuffy that I've seen before include "Airless - pompous" , "Priggish" , "Lacking ventilation; narrow-minded" , "Airless - humourless" , "Badly ventilated" .)