One calling Liverpool fan up about score draw? (7)

I believe the answer is:

dialler

'one calling' is the definition.

'liverpool fan up about score draw?' is the wordplay.
'liverpool fan' becomes 'red' (fan of Liverpool FC).
'up' is a reversal indicator (in down clue: letters go upwards).
'about' is an insertion indicator.
'score draw?' becomes 'iall' (resembles 1 all, or 'one all', a draw in sport).
'red' backwards is 'der'.
'der' placed around 'iall' is 'DIALLER'.

(Another definition for dialler that I've seen is " type of phone software".)

I've seen this clue in The Independent.

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