What does a clock cleaning and oiling entail?

Sometimes when I tell a customer their clock  needs cleaned and oiled, they look at me and sternly tell me that they keep a very clean house!  Keeping your house clean is nice, but a mechanical clock (one that works with a spring that is wound or driven by a weight) needs to have the old oils removed and new oil applied with regularity to keep it in good running condition.  Equate it to this, the oil in the car and/or mower is changed on a regular basis and these items do not run 24 hours a day 365-1/4 days per year.  Not changing the oil in the clock is like having  your car run with the same oil in it for 20 years!  Additionally a clock cleaning and oiling is more than running a dust rag over the brass and spraying the item with lubricant.  A proper cleaning and oiling entails dis-assembly of the movement, polishing the pivots and bearing holes, inspection of the gearing, inspection of the front and back plates, testing of the springs and suspension unit, reassembly, and re-application of the oil that is proper for your movement.  This all takes time and expertise.
A tinkerer can "work on a clock" an horologist understands your clock, how to maintain it, and will provide detailed advice and answers to your questions.  I have a large percentage of my work that comes from "tinkerers" or amateur clock repairers that mostly had good intention but ill planned and conceived work.