You in France wasted years around river mouth (7)
I believe the answer is:
estuary
'river mouth' is the definition.
(I've seen this before)
'you in france wasted years around' is the wordplay.
'you in france' becomes 'tu' ('you' in French).
'wasted' indicates an anagram.
'around' means one lot of letters goes inside another.
'years' is an anagram of 'esary'.
'tu' inserted within 'esary' is 'ESTUARY'.
(Other definitions for estuary that I've seen before include "route to sea" , "Wide part of a river where it nears the sea" , "Broad river mouth" , "River near sea" , "A surety for river mouth" .)