spark, v.² — Green’s Dictionary of Slang

spark v.²

[? SE spark, a beau, i.e. a womanizer, who watches women intently]

(Aus. Und.) to watch carefully.

1901		W.S. Walker In the Blood 113: All you’ve got to do is to be sure o’ your John, an’ learn the time ’e comes round, spark ’im well away, and do yer little does in the blooming hinterval.
1941		Baker Popular Dict. Aus. Sl.
1955		N. Pulliam I Travelled a Lonely Land (1957) 239/2: spark – to stare at carefully, thoroughly.