Green’s Dictionary of Slang

(N.Z. prison) a hypodermic syringe.

2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 67/2: fiddley n. = fiddley and gun.
2001		D. Looser Boobslang [U. Canterbury D.Phil. thesis] 67/2: fiddley and gun n. a hypodermic syringe and needle; also abbreviated to fiddley or gun.