Impractical to abandon mostly toxic rubbish (8)
I believe the answer is:
quixotic
'impractical' is the definition.
('quixotic' can be similar in meaning to 'impractical')
'abandon mostly toxic rubbish' is the wordplay.
'abandon mostly' becomes 'qui' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'rubbish' indicates anagramming the letters.
'toxic' with letters rearranged gives 'xotic'.
'qui'+'xotic'='QUIXOTIC'
'to' is the link.
Can you help me to learn more?
(Other definitions for quixotic that I've seen before include "Fancifully impractical" , "Having impractical ideas" , "Extravagantly romantic" , "Impracticably idealistic" , "Unworldly" .)