Poor Tom is damp (5)
I believe the answer is:
moist
'damp' is the definition.
(I know that damp can be written as moist)
'poor tom is' is the wordplay.
'poor' indicates an anagram.
'tom'+'is'='tomis'
'tomis' is an anagram of 'MOIST'.
(Other definitions for moist that I've seen before include "Slightly wet, damp" , "lubricated" , "Dampish" , "Affected by tears, perhaps" , "sloppy" .)