Heavyweight Tory's arranged robes for the king (8)

I believe the answer is:

royalist

I'm a little stuck... Click here to teach me more about this clue!

'heavyweight tory's' is the definition.
'royalist' can be an answer for 'tory's' (thesaurus). I'm not certain of the 'heavyweight' bit.

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for royalist that I've seen before include "Civil War participant" , "Civil War Cavalier" , "one in civil war" , "Advocate of the principles of monarchy" , "For queen" .)

I've seen this clue in The Times.

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