死んだフリをする (to play dead)
idiom1 sentence
The fixed expression for 'to play dead / feign death.' 死んだ (past attributive of 死ぬ) modifies フリ ('pretense, act'), and the whole is paired with する. The broader pattern is [noun]のフリをする or [verb-past]フリをする = 'to pretend to be/do X.'
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