Immortal who had a way with a piano tune (7)

I believe the answer is:

neptune

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'immortal' is the definition.
(Neptune is an example)

'who had a way with a piano tune' is the wordplay.
'who' becomes 'n' (I can't explain this - if you can you should give a lot more credence to this answer).
'had' means one lot of letters go next to another.
'a way' becomes 'e' (Compass direction - East).
'with' is a charade indicator (letters next to each other).
'a piano' becomes 'p' (musical abbreviation).
'n'+'e'+'p'+'tune'='NEPTUNE'

Can you help me to learn more?

(Other definitions for neptune that I've seen before include "Roman god of water and the sea" , "Poseidon" , "extract from The Planets" , "part of Planets Suite" , "heavenly body" .)

I've seen this clue in the Evening Standard.

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