Muppet who testified before Congress (4)
I believe the answer is:
elmo
'muppet who testified before congress' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for elmo that I've seen before include "Saint whose fire is electric!" , "St ----'s Fire: aura from electrical discharge" , "Puppet character" , "Fiery saint" , "St ...'s fire, weather phenomenon of coloured glow" .)