Green’s Dictionary of Slang

dero n.

also derro
[abbr. + -o sfx (3)]

(Aus./N.Z.) a derelict person, a down-and-out; also as general term of insult; thus attrib.

[US]P. Corris ‘Heroin Annie’ in Heroin Annie [e-book] Outside the shop he shoved his hand into this rubbish bin, like a derro.
[Aus]R. Beckett Dinkum Aussie Dict. 18: Dero: A derelict or down-and-outer who is also probably on the ‘turps’ or ‘meths.’.
[Aus]Tupper & Wortley Aus. Prison Sl. Gloss. [Internet] Derro. An old broken down prisoner. Especially associated with alcoholism. A diminutive of derelict.
[Aus]P. Temple Black Tide (2012) [ebook] Part of it burned down [...] and it served as dero accomodation.
[Aus]P. Temple Dead Point (2008) [ebook] Streets empty, sometimes a dero lying on the pavement.
[NZ] McGill Reed Dict. of N.Z. Sl.
[UK]T. Black Gutted 253: I pointed the way through the winding streets, littered with deros, trash and more than a few needles.