A Democrat stops laughing and beaming (7)
I believe the answer is:
Here is my best explanation:
'beaming' is the definition.
('radiant' can be a synonym of 'beaming')
'a democrat stops laughing' is the subsidiary indication.
'democrat' becomes 'd'.
'stops' is an insertion indicator.
'laughing' becomes 'riant' ('riant' can be a synonym of 'laughing').
'ad' placed into 'riant' is 'radiant'.
'and' is the link.
(Other definitions for radiant that I've seen before include "Brightly glowing", "Luminous", "with good humour", "Sending out light, glowing", "glowing with happiness", "Shining brightly, being at nadir", "beaming with joy", "Glowing brightly", "Straight line" and "Dazzling".)