All evergreen trees will lose one annual set of needles from time to time as more new annual growth occurs. Most often this happens towards mid summer fall as the new needles mature. Interior needles become less productive each year being farther and farther into the interior of the evergreen. Contents of the needles are moved out to more productive parts of the tree and the needles will brown. No you do not have clean out the needles, mother nature does not, so let them fall eventually to the ground below.