Adhesive, gummy (6)
I believe the answer is:
sticky
I believe this is a double definition.
'adhesive' is the first definition.
(similar in meaning)
'gummy' is the second definition.
(synonyms)
(Other definitions for sticky that I've seen before include "Warm and humid" , "Adhesive to the touch" , "Gluey, gooey" , "Oppressive" , "Viscous - problematic" .)