Water collecting in river bay? (5)
I believe the answer is:
horse
'bay?' is the definition.
(bay is a kind of horse)
'water collecting in river' is the wordplay.
'water' becomes 'hose' (water a flowerbed say).
'collecting' means one lot of letters goes inside another.
'in river' becomes 'r' (I can't justify this - if you can you should give a lot more credence to this answer).
'hose' placed around 'r' is 'HORSE'.
Can you help me to learn more?
(Other definitions for horse that I've seen before include "Roan" , "gym apparatus" , "farm animal" , "runner" , "See 13" .)