take a cut; skim off the top; benefit from others' work
Rare expression meaning to profit from someone else's efforts without contributing, or to take a share of the proceeds. Related to 上前をはねる.
See also: 上前をはねる
He never lifts a finger himself and is always thinking only of how to profit from others' work.
The exact derivation is uncertain; 上汁 (うわしる) literally means 'top broth' or 'supernatant liquid,' and the phrase figuratively suggests skimming the best part for oneself.