Cast is entertaining, pocketing 50 grand (5)
I believe the answer is:
flung
'cast' is the definition.
(cast can mean to throw or fling)
'entertaining pocketing 50 grand' is the wordplay.
'entertaining' becomes 'fun' (similar in meaning).
'pocketing' means one lot of letters goes inside another (pocket can mean to steal or take possession of).
'50' becomes 'l' (Roman numeral).
'grand' becomes 'g' (G is short for grand as in a thousand).
'fun' placed around 'l' is 'flun'.
'flun'+'g'='FLUNG'
'is' is the link.
(Other definitions for flung that I've seen before include "Hurled" , "Thrown with force" , "Threw" , "Cast aside" .)