Richter scale blip (6)
I believe the answer is:
tremor
'richter scale blip' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for tremor that I've seen before include "A slight shake, body or earth" , "Involuntary quiver" , "Quavering" , "Nervousness" , "A small shake, perhaps of earth ( 6)" .)