JAPANESE Prime Minister Morihiro Hosokawa will clarify his position on political reform legislation and a proposed economic stimulus package at a Christmas Eve news conference, according to an NHK television news report. The Prime Minister would ''explain'' a campaign pledge to resign if political reform legislation currently pending parliamentary approval was not enacted by year's end, the report said. Mr Hosokawa would also discuss some elements of the Government's as yet undisclosed economic stimulus package, it said. Mr Hosokawa's cabinet has sent out mixed signals on just if and when a stimulus package can be expected. The Government's political reform bill was passed by the lower house of parliament on November 18, but has yet to be approved by the upper house. The political reform bill in its present form will die if it is not passed by the January deadline.