Radiant silver-blue (5)
I believe the answer is:
aglow
'radiant' is the definition.
(I've seen this before)
'silver-blue' is the wordplay.
'silver' becomes 'ag' (Ag is the chemical symbol for silver).
'blue' becomes 'low' (I've seen this in other clues).
'ag'+'low'='AGLOW'
(Other definitions for aglow that I've seen before include "Softly bright or radiant" , "Warm - shiny" , "emitting a steady light" , "Red-hot" , "Shining" .)