Be uncertain about atmospheric dampness and what it may cause (8)
I believe the answer is:
mistrust
'be uncertain' is the definition.
(thesaurus)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for mistrust that I've seen before include "Suspect (someone)" , "Have doubts about" , "Regard with suspicion" , "reservations" , "Have no confidence in (someone)" .)