In Melbourne, Lord Dunglass (Sir Alec Douglas-Home?) gets a duck (3)
I believe the answer is:
pom
'in melbourne lord dunglass' is the definition.
(Australian term for Englishman, eg Lord Dunglass)
'sir alec douglas-home? gets a duck' is the wordplay.
'sir alec douglas-home?' becomes 'pm' (Alec Douglas-Home was a UK prime minister).
'gets' indicates putting letters inside (gets can mean captures or absorbs).
'a duck' becomes 'o'.
'pm' enclosing 'o' is 'POM'.
(Other definitions for pom that I've seen before include "Small dog (colloq.)" , "Little dog" , "Australian term for Englishman" , "Limey in Oz" , "best friend?" .)