Old sailor half involved in wrestling? (6)

I believe the answer is:

nelson

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'wrestling?' is the definition.
Both the definition and answer are singular nouns.
Maybe they are linked in a way I don't understand?

'old sailor half involved' is the wordplay.
'old sailor' becomes 'nels' (I can't explain this - if you can you should believe this answer much more).
'half' means to take half the letters.
'involved' becomes 'in on' (I've seen this in another clue).
'inon' cut in half is 'on'.
'nels'+'on'='NELSON'

'in' is the link.

Can you help me to learn more?

(Other definitions for nelson that I've seen before include "Victorious flag officer" , "Admiral (who had the touch)" , "one visibly affected by fighting" , "mariner with dodgy vision" , "'England expects' admiral" .)

I've seen this clue in the Evening Standard.

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