Glowing or shining
I believe the answer is:
radiant
I believe this clue is a double definition.
'glowing' is the first definition.
(I've seen this in another clue)
'shining' is the second definition.
(I've seen this before)
(Other definitions for radiant that I've seen before include "Very rich (7.2.2)" , "looking happy" , "'Glorious, shining (7)'" , "with good humour" , "Straight line" .)