Crook and prison pal showing how partners may be joined (10)

I believe the answer is:

conjugally

'how partners may be joined' is the definition.
(conjugal means relating to marriage)

'crook and prison pal' is the wordplay.
'crook' becomes 'con'.
'and' means one lot of letters go next to another.
'prison' becomes 'jug' (slang term).
'pal' becomes 'ally' (both can mean a friend or supporter).
'con'+'jug'+'ally'='CONJUGALLY'

'showing' acts as a link.

(Another definition for conjugally that I've seen is " as a wife?".)

I've seen this clue in The Times.

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