Cast worth using (5)
I believe the answer is:
throw
'cast' is the definition.
(synonyms)
'worth using' is the wordplay.
'using' indicates an anagram (the letters used in a different way).
'worth' is an anagram of 'THROW'.
(Other definitions for throw that I've seen before include "Organise party" , "pitch or > floor" , "Deliberately lose" , "Cast, lob" , "shot-put event?" .)