He travels in wet areas (3)
I believe the answer is:
tar
'he travels' 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' says the answer is hidden in the clue.
'TAR' can be found hidden inside 'wet areas'.
Can you help me to learn more?
(Other definitions for tar that I've seen before include "Flammable liquid; sailor" , "It may cover the road" , "Informal sailor or road-surfacing material" , "prepare for feathers?" , "Dark flammable liquid" .)