Try holding tree that's worthless (6)
I believe the answer is:
trashy
'worthless' is the definition.
(trashy can mean of poor quality)
'try holding tree' is the wordplay.
'holding' indicates putting letters inside.
'tree' becomes 'ash' (ash is a kind of tree).
'try' enclosing 'ash' is 'TRASHY'.
'that's' acts as a link.
(Other definitions for trashy that I've seen before include "Shy art - rubbishy" , "Shoddy or ganger" , "Useless" , "As rubbish" , "Futile" .)