Leaves very kind gardener on screen (5)
I believe the answer is:
costa
'screen' is the definition.
Although both the answer and definition are singular nouns, I don't see how they can define each other.
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for costa that I've seen before include "___ Brava, Spanish resort area" , "bone" , "Rib or rib-like structure" , "resort abroad" , "and 5 Down: Spanish holiday destination" .)