Catches in the river and the locals are put out about it (7)
I believe the answer is:
collars
'catches in the river' is the definition.
'collars' can be an answer for 'catches' ('collar' can be a synonym of 'catch'). I'm unsure of the 'in the river' bit.
'the locals are put out about it' is the wordplay.
'are put out' is an anagram indicator.
'about' indicates putting letters inside.
'it' becomes 'r' (I can't explain this - if you can you should give a lot more credence to this answer).
'locals' is an anagram of 'collas'.
'collas' enclosing 'r' is 'COLLARS'.
'and' is the link.
Can you help me to learn more?
(Other definitions for collars that I've seen before include "Grasps" , "Ties with them, perhaps" .)