Supporter adds iron to rum cocktail (5)

I believe the answer is:

femur

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'supporter adds' is the definition.
I can't judge whether this defines the answer.

'iron to rum cocktail' is the wordplay.
'iron' becomes 'Fe' (Fe is the chemical symbol for iron).
'cocktail' indicates an anagram.
'rum' with letters rearranged gives 'mur'.
'fe'+'mur'='FEMUR'

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(Other definitions for femur that I've seen before include "Large bone" , "Thighbone" , "Longest bone in the human body" , "Bone in leg" , "bit of leg" .)

I've seen this clue in The Mirror.

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