Expert handling bad reactions is to go for Parisian meat (9)

I believe the answer is:

allergist

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'expert handling bad reactions is to go' is the definition.
I can't judge whether this defines the answer.

'parisian meat' is the wordplay.
'parisian' becomes 'aller' (I can't explain this - if you can you should believe this answer much more).
'meat' becomes 'gist' (synonyms).
'aller'+'gist'='ALLERGIST'

'for' is the link.

Can you help me to learn more?

(Other definitions for allergist that I've seen before include "Medic" , "expert at medical centre?" .)

I've seen this clue in The Times.

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