腕(うで)が上(あ)がる

うでがあがる
expression
one's skill improves; to get better at
idiom
1. one's skill improves; to get better at
To improve at a skill or craft through practice, such as cooking, a sport or a trade. 腕(うで) here means skill.
料理(りょうり)の腕(うで)が上(あ)がったね。
Your cooking has improved.
By practicing every day, I got better at guitar.
As he kept up his training, his skill as a craftsman improved dramatically.

腕(うで) means skill here, as in 腕(うで)がいい (skilled) and 腕(うで)を磨(みが)く (to hone one's skill).

Common patterns

Watch out

The literal meaning also exists: 肩(かた)が痛(いた)くて腕(うで)が上(あ)がらない (my shoulder hurts so I can't raise my arm).