Washed down a suitable dose at the hospital (5)

I believe the answer is:

hosed

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'washed' is the definition.
(I've seen this before)

I don't understand how the remainder of the clue works.

(Other definitions for hosed that I've seen before include "swilled down with water" , "Watered with a flexible pipe" , "washed" , "wearing tights?" .)

I've seen this clue in the Evening Standard.

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