Peacekeepers restless about sport producing no results (10)

I believe the answer is:

unfruitful

'producing no results' is the definition.

'peacekeepers restless about sport' is the wordplay.
'peacekeepers' becomes 'un'.
'restless' becomes 'fitful'.
'about' means one lot of letters goes inside another.
'sport' becomes 'ru' (rugby union).
'fitful' placed around 'ru' is 'fruitful'.
'un'+'fruitful'='UNFRUITFUL'

(Another definition for unfruitful that I've seen is " Barren".)

I've seen this clue in The Independent.

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