Eco-friendly judge, we hear, finding variety of plum (9)
I believe the answer is:
greengage
'variety of plum' is the definition.
(I've seen this before)
'eco-friendly judge we hear' is the wordplay.
'eco-friendly' becomes 'green' (green can mean good for the environment).
'judge' becomes 'gauge' (synonyms).
'we hear' indicates a 'sounds like' (homophone) clue.
'gauge' sounds like 'gage'.
'green'+'gage'='GREENGAGE'
'finding' is the link.
(Other definitions for greengage that I've seen before include "Fruit akin to plum" , "Garden fruit" , "it's fruity" , "Greenish-yellow type of plum" , "Fruit like a small plum" .)