A tunnel in a dream usually marks a transition you can feel but can't yet see the end of -- moving through something uncertain toward a destination that isn't visible from where you stand. Light appearing ahead can reflect growing confidence that the uncertainty will resolve, even before you know exactly how.
Always deliver judgements from the Stars in general terms, or if thou dost otherwise let it be when thou hast very evident testimonies and in great and weighty matters. - Cardan Girolamo (1501-1576)