Having choice of one side, submit order (4)
I believe the answer is:
sort
'order' is the definition.
(I've seen this before)
'having choice of one side submit' is the wordplay.
'having choice' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'of' becomes 'o'.
'one side' means to remove the middle letters (I've seen 'sides of' mean this (only the letters on the sides remain)).
'submit' becomes 'referforjudgment' ('refer for judgment' can be a synonym of 'submit').
'referforjudgment' with its middle removed is 'rt'.
's'+'o'+'rt'='SORT'
Can you help me to learn more?
(Other definitions for sort that I've seen before include "'Variety, type (4)'" , "Shuffle into desired sequence" , "Arrange systematically" , "Type - arrange in groups" , "Arrange in order" .)