Crossword Genius

Reliable Blue Berets fit into cast (9)

Ross

I believe the answer is:

unfailing

'reliable' is the definition.
(thesaurus)

'blue berets fit into cast' is the wordplay.
'blue berets' becomes 'UN' (United Nations peacekeepers).
'fit' becomes 'AI' (resembles A1, old-fashioned slang for very good).
'into' is an insertion indicator.
'cast' becomes 'fling' (both can mean to throw).
'ai' going into 'fling' is 'failing'.
'un'+'failing'='UNFAILING'

(Another definition for unfailing that I've seen is " Reliable, constant".)

I've seen this clue in The Times.
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