So the reason we both didn't know what Gaffa meant is because its not a word.
I did however find this...
"Gaffa is Katespeak for gaffer tape--duct tape to Americans, but the image isn't supposed to evoke being "stuck," as Kate makes clear: "The idea of the song is that of being given a glimpse of 'God' - something that we dearly want - but being told that unless we work for it, we will never see it again, and even then, we might not be worthy of it. Of course, everybody wants the reward without the toil, so people try to find a way out of the hard work, still hoping to claim the prize, but such is not the case. The choruses are meant to express the feeling of entering timelessness as you become ready for the experience, but only when you are ready."
Also this
