Washed down the wrong dose at the hospital, initially (5)
I believe the answer is:
hosed
'washed down' is the definition.
(I've seen this in another clue)
'wrong dose at the hospital initially' is the wordplay.
'wrong' indicates an anagram.
'at' says to put letters next to each other (I've seen this in other clues).
'initially' says to take the initial letters.
The first letter of 'hospital' is 'h'.
'dose' with letters rearranged gives 'osed'.
'osed' put after 'h' is 'HOSED'.
'the' is the link.
(Other definitions for hosed that I've seen before include "swilled down with water" , "wearing tights?" , "washed" , "Watered with a flexible pipe" .)