费工夫

工夫 (gōngfu, here neutral tone in 'fu') means 'time/effort spent.' Don't confuse with 功夫 (gōngfu, 'kungfu / skill') - they're often interchangeable in modern usage but in the phrase 费工夫, the time-and-effort sense dominates. The opposite is 省工夫 (shěng gōngfu, 'to save effort').

grammar

Often used with 很 (hěn) or 真 (zhēn) before it: 很费工夫 / 真费工夫. Can also take an object via 在: 在这件事上费工夫 ('to put effort into this matter').