22 across
Is
the
cause
of
stories
behind
two
foreign
articles
(9)
Is the cause of stories behind two foreign articles (9)
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The definition is at the beginning of the clue.
How the clue works
Right, so is the cause of is your definition there, meaning to underlie something, be the reason behind it. For the wordplay, you want "stories" placed after two foreign articles - UN, the French word for "a", and DER, the German word for "the" - so you're stacking UN then DER then LIES (the stories) to build the whole thing.