Rafter displays ray of light (4)
I believe the answer is:
beam
I believe this clue is a double definition.
'rafter' is the first definition.
(thesaurus)
'ray of light' is the second definition.
(synonyms)
'displays' is the link.
(Other definitions for beam that I've seen before include "Smile; wooden supporter?" , "Smile radiantly" , "Ray; structural timber" , "Smile, light shaft" , "XWD SETTER" .)