Good thing for Aussie, heading off, about to go to a restaurant (3,3)
I believe the answer is:
eat out
'go to a restaurant' is the definition.
(as opposed to eating at home)
'good thing for aussie heading off about to' is the wordplay.
'good thing for aussie' becomes 'beaut' (informal Australian term for a very good thing).
'heading off' means to remove the first letter.
'about' means one lot of letters goes inside another.
'beaut' with its initial letter removed is 'eaut'.
'eaut' placed around 'to' is 'EAT OUT'.
(Other definitions for eat out that I've seen before include "Lunch in pub?" , "Visit a restaurant" , "Use a restaurant" , "'Don't dine at home (3,3)'" , "Dine in restaurant rather than home" .)