Dutch colonist welcomes Australian pub (6)
I believe the answer is:
boozer
'pub' is the definition.
(boozer can informally mean a pub)
'dutch colonist welcomes australian' is the wordplay.
'dutch colonist' becomes 'boer' (I've seen this in another clue).
'welcomes' means one lot of letters goes inside another (in sense of 'invites in').
'australian' becomes 'Oz' (nickname for Australia).
'boer' enclosing 'oz' is 'BOOZER'.
(Other definitions for boozer that I've seen before include "Pub (slang)" , "Inn" , "Pub (sl.)" , "Heavy drinker" .)