Outwardly river police, as you choose? (6)
I believe the answer is:
decide
'choose?' is the definition.
(choosing is a kind of deciding)
'outwardly river police as' is the wordplay.
'outwardly' means to remove the middle letters (only the outermost letters are used).
'river' becomes 'dee' (River Dee).
'police' becomes 'cid'.
'as' becomes 'e' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'dee' with its middle removed is 'de'.
'de'+'cid'+'e'='DECIDE'
'you' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for decide that I've seen before include "Come to a resolution" , "Resolve, settle (issue)" , "Choose" , "Determine - settle" , "Adjudicate" .)