Radar signal (4)
I believe the answer is:
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">radar signal</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is all the clue.<br/ ></span>
(Other definitions for blip that I've seen before include "Temporary irregularity" , "Small mark - unforeseen deviation" , "Signal on a radar screen" , "shows up on radar screen" , "often seen on radar screen" .)