A little light from Rigel flickered around 2000 (7)
I believe the answer is:
glimmer
'a little light' is the definition.
(a glimmer is a faint light)
'rigel flickered around 2000' is the wordplay.
'flickered' indicates anagramming the letters (I've seen 'flickering' mean this (I've seen this in other clues)).
'around' indicates putting letters inside.
'2000' becomes 'MM' (2000 in Roman numerals).
'rigel' with letters rearranged gives 'glier'.
'glier' placed around 'mm' is 'GLIMMER'.
'from' acts as a link.
(Other definitions for glimmer that I've seen before include "Gleam faintly, like candle in dark" , "Faint wavering light" , "Shine faintly with a wavering light" , "Faint glow" , "Shine faintly and waveringly" .)