Dispatch, say, about 50 (4)
I believe the answer is:
slay
'dispatch' is the definition.
(synonyms)
'say about 50' is the wordplay.
'about' indicates putting letters inside.
'50' becomes 'l' (Roman numeral).
'say' enclosing 'l' is 'SLAY'.
(Other definitions for slay that I've seen before include "Kill with premeditation" , "Kill, murder" , "Massacre" , "Violently kill" , "Fatally hit" .)