Wiktionary
conj. (non-gloss definition: Introduces an unexpected situation that renders the aforementioned effort inadequate or irrelevant.)
Usage examples of "only for".
He was held responsible only for the safety of his chains, and for the rest was at the mercy of his gaoler.
It was not, perhaps, so pleasant as under the awning on the poop-deck, but that sacred shade was only for such great men as the captain and his officers, Surgeon Pine, Lieutenant Maurice Frere, and, most important personages of all, Captain Vickers and his wife.
Despite their age, he still feared them, if only for the fact that they had apparently managed to capture Pip, a feat beyond the capabilities of most.
It was visible only for seconds, though in that time it filled the entire chamber.
My contact is in place at the border, but only for another two hours.
Everything looked so ordinary, but only for the moment and only as far as I could see.
Since the Chamber budget allowed only for a once-a-month lunch in the conference room, supernumerary sessions were held in the Inn's Lounge.