Useless son finds clothes (4)
I believe the answer is:
'clothes' is the definition.
(duds is a kind of clothes)
'useless son' is the wordplay.
'useless' becomes 'dud' (dud can mean faulty or failing).
'son' becomes 's' (genealogical abbreviation for son).
'finds' acts as a link.
(Other definitions for duds that I've seen before include "One assumes them" , "Failures; clothes" , "Bombs that fail to explode" .)