Fish do get caught by rising (3)
I believe the answer is:
cod
'fish' is the definition.
(type of fish)
'do get caught by rising' is the wordplay.
'get' is a charade indicator (letters next to each other).
'caught by' becomes 'c' (cricket abbreviation. I am not sure about the 'by' bit.).
'rising' shows that the letters should be reversed in order (in a down clue, letters go up).
'do'+'c'='doc'
'doc' backwards is 'COD'.
Can you help me to learn more?
(Other definitions for cod that I've seen before include "North Atlantic fish" , "Cash on delivery for hoax" , "to be paid for when it arrives" , "Fish noted for liver oil" , "Initially, pay when you receive the goods" .)