One aims to shoot bird by river (6)

I believe the answer is:

sniper

I'm a little stuck... Click here to teach me more about this clue!

'one aims to shoot' is the definition.
I know that 'shoot' relates to this answer.

'bird by river' is the wordplay.
'bird' becomes 'snipe' (snipe is a kind of bird).
'by river' becomes 'r' (abbreviation. I am not sure about the 'by' bit.).
'snipe'+'r'='SNIPER'

Can you help me to learn more?

(Other definitions for sniper that I've seen before include "Lone rifleman" , "Hidden sharpshooter" , "He shoots from hiding-place" , "Hidden marksman" , "Individual firing from cover" .)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.