Medicament required when one has duck to eat? (6)
I believe the answer is:
iodine
'medicament' is the definition.
(iodine is a kind of medicament)
'one has duck to eat?' is the wordplay.
'one' becomes 'i' (Roman numeral).
'has' means one lot of letters go next to another.
'duck' becomes 'o' (resembles zero - 'duck' in cricket).
'to eat?' becomes 'dine' (to dine is to eat a meal).
'i'+'o'+'dine'='IODINE'
'required when' is the link.
(Other definitions for iodine that I've seen before include "Element forming black crystals or violet vapour" , "Disinfectant made from seaweed" , "Element, atomic number 53" , "Black crystalline element" , "Element that can exist as a purple vapour" .)