Island valley, not area offering no fruit? (4)

I believe the answer is:

idle

'offering no fruit?' is the definition.
(something idle is unproductive or not fruitful)

I don't understand the rest of the clue.

(Other definitions for idle that I've seen before include "staying in bed all day?" , "without purpose" , "-- Jack, pantomime character" , "Not in active use" , "Run out of gear" .)

I've seen this clue in The Times.

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