Medicament required when one has nothing to eat? (6)
I believe the answer is:
iodine
'medicament' is the definition.
(iodine is a kind of medicament)
'one has nothing to eat?' is the wordplay.
'one' becomes 'i' (Roman numeral).
'has' says to put letters next to each other.
'nothing' becomes 'O' (looks like zero - 0).
'to eat?' becomes 'dine' (to dine is to eat a meal).
'i'+'o'+'dine'='IODINE'
'required when' acts as a link.
(Other definitions for iodine that I've seen before include "Antiseptic made from seaweed" , "Halogen element, atomic no 53" , "Element used in medicine, photography and dyes" , "Black/violet element" , "Element existing in vapour and crystalline form" .)