noun
tedious job; time-consuming work; piecework
Refers to work that takes a lot of time and effort, often manual or detailed. Can also mean piecework, where pay is based on the amount produced rather than time spent.
この刺繍は手間仕事だから、完成までに一ヶ月かかる。
This embroidery is a time-consuming job, so it will take a month to finish.
内職で手間仕事を請け負っ
I take on piecework as a side job.
Compound of 手間 (てま, 'time and effort') and 仕事 (しごと, 'work'). The exact historical derivation is uncertain, but the meaning is transparent from its components.