No real cowboy strikes a false note (4)

I believe the answer is:

dude

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

'cowboy strikes a false note' is the definition.
I can't tell whether this definition defines the answer.

'no real' is the wordplay.
'no' becomes 'dud' (I can't justify this - if you can you should believe this answer much more).
'real' becomes 'e' (e is a kind of real).
'dud'+'e'='DUDE'

Can you help me to learn more?

(Other definitions for dude that I've seen before include "He's no cowboy" , "American bloke" , "Stylish and affected man" , "Man (American slang)" , "A (dandy) American city dweller" .)

I've seen this clue in the Evening Standard.

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