Rash insiders cut a flower (5)
I believe the answer is:
rhone
'flower' is the definition.
(River Rhone, something which flows)
'rash insiders cut a' is the wordplay.
'rash insiders cut' becomes 'rh' (I can't explain this - if you can you should give a lot more credence to this answer).
'a' becomes 'one'.
'rh'+'one'='RHONE'
Can you help me to learn more?
(Other definitions for rhone that I've seen before include "River running through France to the Med" , "12 wine region" , "Major French river, rising in Switzerland" , "wherein runs rain in Arbroath" , "River of Switzerland and France" .)