Short film of a misdirected retrial (7)
I believe the answer is:
trailer
'short film' is the definition.
(I've seen this before)
'a misdirected retrial' is the wordplay.
'a misdirected' indicates anagramming the letters (I've seen this in other clues).
'retrial' is an anagram of 'TRAILER'.
'of' is the link.
(Other definitions for trailer that I've seen before include "Picture" , "Appetising extract" , "farm vehicle" , "one's dragged behind" , "Film advertisement" .)