Laugh to behold a ring (4)
I believe the answer is:
halo
'a ring' is the definition.
(I know that ring can be written as halo)
'laugh to behold' is the wordplay.
'laugh' becomes 'ha' ().
'to behold' becomes 'lo' (archaic exclamation meaning 'look!').
'ha'+'lo'='HALO'
(Other definitions for halo that I've seen before include "Saint's headlight?" , "Aura representing saintliness" , "Band of light" , "Ring of saintliness" , "Saint's overhead ring of light" .)