Grin, beam (5)
I believe the answer is:
smile
I believe this clue is a double definition.
'grin' is the first definition.
(synonyms)
'beam' is the second definition.
(I know that beam is a more specific form of smile)
(Other definitions for smile that I've seen before include "Pleased expression" , "Indicate pleasure with lips movement" , "Look happy" , "Show happiness" , "Show amusement or pleasure" .)