Wiktionary
a. (context UK slang English) Begging, making requests for loans. (from early 20th c.)
Usage examples of "on the tap".
She got up and went into the bathroom and turned on the tap before remembering that there was something she still had to do.
Then all I have to do is turn on the tap and watch the money pour in.
I started work that afternoon, reviewing the technical literature on the TAP implant -- the closest thing to an objective account of its capabilities I was likely to find.
To Jack's left, a woman was talking earnestly on the Tap's pay phone - a phone Jack would never touch again if he had his way about it, not for a thousand dollars.
Skiller rushed past his wife and laid a hand on the tap of the nearest barrel.
My labor was to take more than fifty steps through the burning sand, looking neither to left nor right, to climb the still more burning steps to the bathhouse, to turn on the tap, to twist my head and hold my mouth under it, to drink, to rinse, to swallow in order that Oskar might be replenished.
He leaned over the sink and dry heaved again, and turned on the tap to splash his face with cold water—.