Wettish mark in person’s home comes back (4)
I believe the answer is:
damp
'wettish' is the definition.
(thesaurus)
'mark in person's home comes back' is the wordplay.
'mark' becomes 'm'.
'in' indicates putting letters inside.
'person's home' becomes 'pad'.
'comes back' shows that the letters should be reversed in order.
'm' inserted within 'pad' is 'pmad'.
'pmad' back-to-front is 'DAMP'.
(Other definitions for damp that I've seen before include "Humid" , "Rising -, TV sitcom" , "dripping" , "soggy" , "Moist air" .)