Batting partner, one who's gone down (6)

I believe the answer is:

inmate

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'one who's gone down' is the definition.
I can't tell whether this defines the answer.

'batting partner' is the wordplay.
'batting' becomes 'in'.
'partner' becomes 'mate' ('mate' can be a synonym of 'partner').
'in'+'mate'='INMATE'

Can you help me to learn more?

(Other definitions for inmate that I've seen before include "you mightn't want him to escape" , "One is confined to an institution" , "Institution resident" , "eg Prisoner" , "Con" .)

I've seen this clue in The Telegraph.

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