Cast shortened the series (5)
I believe the answer is:
throw
'cast' is the definition.
('throw' can be a synonym of 'cast')
'shortened the series' is the wordplay.
'shortened' means to remove the last letter.
'series' becomes 'row' (I've seen this before).
'the' with its final letter taken away is 'th'.
'th'+'row'='THROW'
(Other definitions for throw that I've seen before include "lose on purpose" , "Sling" , "return from the boundary, perhaps" , "Discard" , "shot-put event?" .)