Portion of green plant served at table (6)
I believe the answer is:
entree
'portion' is the definition.
(thesaurus)
'green plant served at table' is the wordplay.
I cannot quite see how this works, but
'plant' could be 'tree' and 'tree' is found in the answer.
The remaining letters 'en' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
'of' is the link.
Can you help me to learn more?
(Other definitions for entree that I've seen before include "The right of admission or entry" , "Dish allowing one to go in?" , "Main course dish" , "No way-out" , "Right of entrance for a dish?" .)