Funniness about a delay (4)
I believe the answer is:
wait
'delay' is the definition.
(I know that delay can be written as wait)
'funniness about a' is the wordplay.
'funniness' becomes 'wit' (being witty).
'about' indicates putting letters inside.
'wit' enclosing 'a' is 'WAIT'.
(Other definitions for wait that I've seen before include "singer" , "Linger, delay" , "Attend, expect" , "Linger behind" , "Delay action" .)