Silicon filtered out of rank medicinal drink (6)
I believe the answer is:
potion
'medicinal drink' is the definition.
(I've seen this before)
'silicon filtered out of rank' is the wordplay.
'silicon' becomes 'si' (Si is the chemical symbol for silicon).
'filtered out of' is a deletion indicator.
'rank' becomes 'position' (I've seen this before).
'position' with 'si' taken away is 'POTION'.
(Other definitions for potion that I've seen before include "Magic concoction" , "Option of a liquid medicine" , "Witch's brew" , "Draught of medicine" , "Concoction - elixir" .)