Killing provides singular merriment (9)
I believe the answer is:
slaughter
'killing' is the definition.
(I know that slaughter is a type of killing)
'singular merriment' is the wordplay.
'singular' becomes 's' (abbreviation sometimes used in dictionaries).
'merriment' becomes 'laughter' (I've seen this before).
's'+'laughter'='SLAUGHTER'
'provides' is the link.
(Other definitions for slaughter that I've seen before include "Kill (animals) for food" , "Mass killing or carnage" , "best" , "in which many die" , "Murder" .)