Worthless tree-hugging endeavour (6)
I believe the answer is:
trashy
'worthless' is the definition.
(trashy can mean of poor quality)
'tree-hugging endeavour' is the wordplay.
'tree' becomes 'ash' (ash is a kind of tree).
'hugging' means one lot of letters goes inside another (inserted letters are hugged).
'endeavour' becomes 'try' (synonyms).
'ash' put inside 'try' is 'TRASHY'.
(Other definitions for trashy that I've seen before include "Cheap and nasty" , "Cheap and worthless" , "Of poor quality" , "As rubbish" , "Useless" .)