Fish squirted water from mouths across river (5)
I believe the answer is:
sprat
'fish' is the definition.
(sprat is a kind of fish)
'squirted water from mouths across river' is the wordplay.
I cannot really understand how this works, but
'river' could be 'r' (abbreviation for river) and 'r' is located in the answer.
'water' could be 'spa' (I've seen this before) and 'spa' is found in the leftover letters.
A single letter 't' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for sprat that I've seen before include "Jack, perhaps" , "Young herring" , "It's set to catch a mackerel" , "Jack --, non-fat eater" , "Couple sharing meat" .)