It means that the clockwork inside the clock functions properly, and the chimes that announce the hours (and possibly the quarter hours) go off properly, but that the hour hand does not move.
In this image, you can see a long "hand" (an indicator) which is the minute hand, and which is pointing at the two--indicating that it is ten minutes past the hour. Note the five division between each number, which indicate the minutes. The short "hand" is the hour hand, and in this image it is pointing toward the ten. That means that it is ten minutes past ten.
So the lady is saying that it strikes well and hearty--meaning that the chimes which indicate the hour (and possibly the quarter hours) strike, that is to say, sound at the proper time, and sound loudly. However, the hour hand does not move.