Something green found in empty doorway is fake (5)
I believe the answer is:
decoy
'fake' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'something green found in empty doorway' is the wordplay.
'something green' becomes 'eco' (I can't explain this - if you can you should give a lot more credence to this answer).
'found in' indicates putting letters inside.
'empty' says to hollow out the word (remove centre letters).
'doorway' with its middle taken out is 'dy'.
'eco' placed inside 'dy' is 'DECOY'.
'is' is the link.
Can you help me to learn more?
(Other definitions for decoy that I've seen before include "Something used to lure prey into a trap" , "Inveigle" , "It's used to lead into a trap" , "Entrap" , "Thing used to lure animal into trap" .)