Tom is horribly damp (5)
I believe the answer is:
moist
'damp' is the definition.
(I know that damp can be written as moist)
'tom is horribly' is the wordplay.
'horribly' indicates anagramming the letters (a horribly wrong version of the letters).
'tom'+'is'='tomis'
'tomis' with letters rearranged gives 'MOIST'.
(Other definitions for moist that I've seen before include "Dampish" , "Affected by tears, perhaps" , "lubricated" , "Slightly wet, damp" , "bit wet" .)