As you know, Meerana, we need context to reliably answer these questions. Where did you find this term?
It sounds like some kind of old-fashioned word for a woman who serves cider in an inn. If you look up both "cider" and "wench", you will likely grasp the meaning. Calling a woman in a similar position today a "ciderwench" would likely be offensive to her, although it might be done jokingly.