To bear fruit means to yield results, which is what the training is beginning to do according to the reports.
Consider the statement "As reports trickle in from the scattered settlements, it becomes clear that the varangian military training is beginning to yield results.". Based on this "As reports trickle in from the scattered settlements, it becomes clear that the varangian military training is beginning to bear fruit." a true statement? Yes, no, or I don't know?