Cough mixture (12)
'cough mixture' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for linctus that I've seen before include "Special formulation" , "Cough medicine" , "Cough-medicine" , "Soothing drink" , "Thick liquid medicine" .)
(Other definitions for decongestant that I've seen before include "cold remedy" , "Catarrh reliever" , "Medicine to unblock the nose" , "Medicine clearing airways" .)