He does his job in wet areas (3)
I believe the answer is:
tar
'he does his job' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'in wet areas' is the wordplay.
'in' indicates a hidden word.
'TAR' is hidden in the letters of 'wet areas'.
Can you help me to learn more?
(Other definitions for tar that I've seen before include "Hearty" , "Mariner, old salt" , "Pitch; sailor" , "Dark viscous flammable substance" , "Tobacco residue; sailor" .)