Argumentative defender I grabbed by attacked goalpost (9)

I believe the answer is:

apologist

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'argumentative defender' is the definition.
'apologist' can be an answer for 'defender' (I've seen this before). I am unsure of the 'argumentative' bit.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for apologist that I've seen before include "Someone arguing" , "Justifier" , "Person who argues to defend or justify some policy" , "Advocate" , "One who argues in favour of something controversial" .)

I've seen this clue in The Sunday Times.

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