Our moves keeping Juliet from Romeo? I determine the guilty party (5)
I believe the answer is:
juror
'i determine the guilty party' is the definition.
'our moves keeping juliet from romeo?' is the wordplay.
'moves' indicates an anagram.
'keeping' indicates putting letters inside.
'juliet' becomes 'j' (phonetic alphabet: alpha, bravo, charlie etc.).
'from' means one lot of letters go next to another.
'romeo?' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'our' anagrammed gives 'uro'.
'uro' placed around 'j' is 'juro'.
'juro'+'r'='JUROR'
(Other definitions for juror that I've seen before include "One of twelve in a box?" , "One empanelled in court" , "One of those responsible for verdict" , "One in box in court" , "Trial panellist" .)