Worthless mush or fond indefinite article (4-3-7)
I believe the answer is:
good-for-nothing
'worthless' is the definition.
(similar in meaning)
'mush or fond indefinite article' is the wordplay.
I cannot really see how this works, but
'mush' could be 'goo' (I've seen this in another clue) and 'goo' is located in the answer.
'or' is found in the answer.
an anagram of 'fond' is 'dfno' which is present in the left over letters.
'article' could be 'thing' (both can mean an object) and 'thing' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for good-for-nothing that I've seen before include "Worthless person" , "Ultimate sale bargain" , "Waster" .)