Humid (6)
'humid' is the definition.
(muggy can mean humid or close)
This is all the clue.
(Other definitions for muggy that I've seen before include "Oppressively humid" , "close" , "Warm and wet" , "Unpleasantly humid" , "Damp and stifling" .)
'humid' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for steamy that I've seen before include "Hot and misty" , "Salacious" , "Erotic; like vapour" , "Full of vapour; erotic (book)" , "Torrid, erotic" .)
'humid' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for sultry that I've seen before include "Such weather is close and oppressive" , "Hot, close (weather)" , "Such weather is hot and oppressive" , "Oppressively hot and humid" , "Close -- sensual" .)
(Other definitions for tropical that I've seen before include "Hot and humid, near the equator" , "Relating to hot and humid parts" , "Boiling" , "Describes weather that is hot and humid" , "Fervidly hot" .)