Wiktionary
a. (context legal English) Pertaining to a test of causation whereby an agent or action is considered to have caused an event (and therefore to be responsible and/or liable for said event) if, had said agent or action not existed, the event would not have taken place. prep. except, except for, not counting; were it not for.
Usage examples of "but for".
She supposed that the rain would drive people indoors once it started, but for now just about everybody on the street was out, gawking down the hill at Entragian's house.
It'll be gone in another ten or fifteen seconds, he knows, driven to earth and then washed away by the pounding rain, but for the time being it's still there, as if to keep him from even trying to believe it was all just a hallucination .
That might come back to haunt her later if there was a later but for now .
There was a taste on his skin, just the taste of his own sweat, of course, but for a moment it seemed almost to be the taste of pussy, and he leaned forward, sure he was going to vomit.
At first that had been a problem, maybe the first real one of Steve's adult life, but for some reason he had stuck with it in spite of his fear of fucking up and being lynched by drunk cycle-wolves.
Just thinking about that kind of food usually nauseates him, but for the moment the image holds in his mind, he is desperately hungry.
I know it's not real, & that I've got all this mess to come back to, but for the time I'm there, none of that matters.
I feed it, I buy the new MotoKops toys it wants (and the comic books, of course, which I must read to it because Seth doesn't have that skill for it to draw on), but for that other purpose I am useless.
After that he was not in the least put off by the odd dress and odd manners of his clients (Thomas gave him the full treatment, with benedictions thrown in, aware that Konsky would discount it but for the purpose of staying in character).