A clone should remain on the same light cycle that the donor plant was being grown under. So if the donor or mother plant was under 24hours light then clone under 24hours light. If the Donor or mother plant was on 20/4 or 18/6 then use 20/4 or 18/6.
Once rooted you can flower it straight away if you want. Some people do this as a SOG and have a perpetual cycle of small single cola plants.