Deliberate Practice is a term from Eric Ericsson describing practice that is not mere repetition of a task, but rather focused intently on the parts of a task which need attention. According to Ericsson’s research, many people treat practice as a rehearsal of the target activity, but elite performers break down the activity into logical parts and spend time targeting problem areas.
As an example, you might consider a violin player. A violin player who practices in a normal way might play a piece they need to master 20 times in the space of two hours. An elite performer might use deliberate practice: playing problem phrases, playing it faster than normal, slower than normal, playing every other note, playing it backwards — anything to keep the level of difficulty high.
In effect, Deliberate Practice is a sort of reverse scaffolding. See Deliberate Practice as Reverse Scaffolding