Display Screen or Portion Thereof with a Graphical User Interface for Showing an Alarm Feature

FIG. 1 is a front view of a display screen or portion thereof with a graphical user interface for showing an alarm feature, showing a first image in a sequence in accordance with our new design; and, FIG. 2 is a second image thereof. The appearance of the animated graphical user interface sequentially transitions between the images shown in FIG. 1 - 2 . The process or period in which one image transitions to another image forms no part of the claimed design. The outermost broken line in the figures illustrates a display screen or portion thereof. The remaining broken lines illustrate portions of the graphical user interface. None of the broken lines form part of the claimed design.