chip (away) at (something)
1. Literally, to break off fragments of something. We won't be able to move this huge rock until we chip at it and make it smaller.
2. By extension, to complete small, incremental portions of a task. I knew I wouldn't be able to write 50 pages in one night, so I've been chipping away at this paper for a few weeks.
chip (away) at something
to break off tiny pieces of something little by little. The mason chipped away at the bricks. He chipped at the block of marble gently.