Crossword Genius

Hidden gunman finds bird by river (6)

Ross

I believe the answer is:

sniper

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

'hidden gunman' is the definition.
(I've seen this in another clue)

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

'finds' acts as a link.

Can you help me to learn more?

(Other definitions for sniper that I've seen before include "Individual firing from cover" , "Concealed shooter" , "Critic" , "Hidden marksman" , "One aiming" .)

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