Ray and Maureen, getting on, smile (8)
I believe the answer is:
moonbeam
'ray' is the definition.
(moonbeam is a kind of ray)
'maureen getting on smile' is the wordplay.
'maureen' becomes 'mo' (I've seen this in other clues).
'getting' is a charade indicator (letters next to each other).
'smile' becomes 'beam' (beaming is a kind of smiling).
'mo'+'on'+'beam'='MOONBEAM'
'and' acts as a link.
(Other definitions for moonbeam that I've seen before include "reflective illumination" , "Pale ray of light" , "Night shiner" , "A lunar ray of light" , "Night light?" .)