Drink anything provided by doctor (7)
I believe the answer is:
draught
'drink' is the definition.
(I know that draught is a type of drink)
'anything provided by doctor' is the wordplay.
'anything' becomes 'aught' ('aught' means anything).
'provided by' is a charade indicator (letters next to each other).
'doctor' becomes 'dr' (abbreviation).
'aught' after 'dr' is 'DRAUGHT'.
(Other definitions for draught that I've seen before include "Water depth; served from a cask" , "unwelcome arrival under the door?" , "ship needs so much water?" , "Swallow" , "It may be drunk" .)