Suspect signs of damp and decay? (8)
I believe the answer is:
mistrust
'suspect' is the definition.
(I know that suspect can be written as mistrust)
'signs of damp and decay?' is the wordplay.
'signs of damp' becomes 'mist' (mist might suggest dampness).
'and' is a charade indicator (letters next to each other).
'decay?' becomes 'rust' (rusting is a kind of decaying).
'mist'+'rust'='MISTRUST'
(Other definitions for mistrust that I've seen before include "Have no confidence in (someone)" , "Lack of belief (in someone)" , "Have doubts about" , "reservations" , "Suspect (someone)" .)