Refuse initial treatment for reaction to poison ivy (5)

I believe the answer is:

trash

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'refuse' is the definition.
(I know that refuse can be written as trash)

I don't understand the rest of the clue.

(Other definitions for trash that I've seen before include "Rubbish, refuse" , "Condemn" , "Take the tops from < rhubarb" , "pulp" , "Drivel" .)

I've seen this clue in The Irish Times.

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