Poor quality tree entered in test (6)
I believe the answer is:
trashy
'poor quality' is the definition.
(trashy can mean of poor quality)
'tree entered in test' is the wordplay.
'tree' becomes 'ash' (ash is a kind of tree).
'entered in' indicates putting letters inside.
'test' becomes 'try' (synonyms).
'ash' inserted within 'try' is 'TRASHY'.
(Other definitions for trashy that I've seen before include "Of no value or quality" , "Shoddy or ganger" , "Cheap and badly made" , "Poorly made" , "Shoddy and worthless" .)