Biblical character: “I am upset about men serving over Christmas period?” (8)

I believe the answer is:

mordecai

'biblical character' is the definition.

'i am upset about men serving over christmas period?' is the wordplay.
'upset' is a reversal indicator.
'about' is an insertion indicator.
'men serving' becomes 'or' (military abbreviation for Other Ranks).
'over' says to put letters next to each other.
'christmas period?' becomes 'dec' (December).
'i'+'am'='iam'
'iam' backwards is 'mai'.
'or'+'dec'='ordec'
'mai' enclosing 'ordec' is 'MORDECAI'.

I've seen this clue in The Independent.

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