Close, muggy (5)
I believe the answer is:
humid
This clue is a double definition.
'close' is the first definition.
(I've seen this before)
'muggy' is the second definition.
(synonyms)
(Other definitions for humid that I've seen before include "Sultry" , "'Moist, damp (5)'" , "Moist, warm (weather)" , "Muggy" , "Damp and warm" .)