Therefore strange mist causes sickness (8)

I believe the answer is:

ergotism

'sickness' is the definition.
(ergotism is a kind of sickness)

'therefore strange mist' is the wordplay.
'therefore' becomes 'ergo' (I've seen this before).
'strange' is an anagram indicator.
'mist' is an anagram of 'tism'.
'ergo'+'tism'='ERGOTISM'

'causes' is the link.

(Another definition for ergotism that I've seen is " fungal disease".)

I've seen this clue in The Independent.

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