Dispatch, say, about fifty (4)
I believe the answer is:
slay
'dispatch' is the definition.
(I know that dispatch can be written as slay)
'say about fifty' is the wordplay.
'about' indicates putting letters inside.
'fifty' becomes 'l' (Roman numeral).
'say' going around 'l' is 'SLAY'.
(Other definitions for slay that I've seen before include "Kill (literary)" , "Kill intentionally" , "Kill with premeditation" , "Destroy" , "Violently kill" .)