Meteorological effect of moving online (2,4)
I believe the answer is:
el nino
'meteorological effect' is the definition.
(El Nino is a weather phenomenon)
'moving online' is the wordplay.
'moving' is an anagram indicator.
'online' anagrammed gives 'EL NINO'.
'of' acts as a link.
(Other definitions for el nino that I've seen before include "modern opera" , "Periodical Pacific weather phenomenon" , "Pacific feature affecting climate" , "Disrupter of weather patterns" , "Warming Pacific current" .)