Green’s Dictionary of Slang

(Aus.) a public house that opens earlier than the general time.

[1880		Sydney Mail 4 Apr. 736/3: The sleeper awakened passes shakily along, looking around for an early opening pub where he can steady his nerves with ‘a hair of the dog that bit him’].
1979		Aus. Women's Wkly 12 Dec. 76/2: Like many ‘early opener’ towns, it is possible to drink right through the day and into the night.
1986		LiNQ 14-15 67: There are old smells of stale ash and beer on fingers as they wind around the glasses at the harbour early opener. The lights are dull and cast deep shadows over the faces of the night shift.
1996		J. Byrell Lairs, Urgers & Coat-Tuggers 96: [H]e and Jimmy Ah Poon sauntered across the road to the noisome old Burlington early-opener rubbady for a brace of schooners during their morning-tea break.
2012		G. Richards (con. 1930s) Great Aus. Super-hero 14: The early opener - a pub near the wharves with an official license to open at 6am to cater for the all night shift workers, was also known affectionately as ‘The Arthur Morris’ who opened the batting for Australia [...] in the 1930s.