on the fiddle

Prepositional phrase

Engaged in financially dishonest behaviour.

Japanese Meaning

金銭にまつわる不正行為に携わっている / 財務上の詐欺や横領などの不正を行っている

The charity's treasurer was on the fiddle, siphoning donations into a private account for years.

その慈善団体の会計担当者は詐欺を働き、何年も寄付金を私的な口座に流していた。

Sense（1）

Engaged in financially dishonest behaviour.

He can't possibly afford that house on his salary. He must be on the fiddle.