Terrified by a concoction for roughage (7,5)

I believe the answer is:

dietary fibre

'roughage' is the definition.
(eating fibre creates roughage)

'terrified by a concoction' is the wordplay.
'concoction' is an anagram indicator.
'terrified'+'by'+'a'='terrifiedbya'
'terrifiedbya' anagrammed gives 'DIETARY FIBRE'.

'for' is the link.

I've seen this clue in The Guardian.

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