。
She set the clock 10 minutes fast.
Literal
She [topic-は] clock [object-を] 10-minutes made-advance.
進ませた is the causative of the intransitive 進む ('advance, go forward'): 'caused (the clock) to advance.' The transitive 進める would have given the same meaning more directly (時計を１０分進めた = 'advanced the clock 10 minutes'). Japanese frequently has both options — making the causative of an intransitive verb when a transitive equivalent already exists. The two are not always interchangeable, but for clocks the difference is subtle. Setting one's watch a few minutes fast as a self-trick to avoid lateness is a near-universal life hack — including in Japan, where punctuality is taken seriously.