Smile, Ray! (4)
I believe the answer is:
beam
I believe this clue is a double definition.
'smile' is the first definition.
(beam can mean to smile)
'ray' is the second definition.
(I know that ray can be written as beam)
(Other definitions for beam that I've seen before include "Give a wide smile" , "Piece of timber - shaft of light" , "Radiant smile; timber support" , "Ship's width; ray" , "Wide grin" .)