Beloved red monster (4)
I believe the answer is:
elmo
(Other definitions for elmo that I've seen before include "Sesame Street character - patron saint of sailors (with his own fire)" , "St ...'s fire, weather phenomenon of coloured glow" , "Puppet character" , "Saint whose "fire" occurs around masts etc" , "St ----'s Fire: aura from electrical discharge" .)