Rum produced in Roman lab (8)

I believe the answer is:

abnormal

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

'rum' is the definition.
(I've seen this before)

'in roman lab' is the wordplay.
'roman lab' can be anagrammed to 'ABNORMAL'.
However, I am not sure how this is indicated.

'produced' is the link.

Can you help me to learn more?

(Other definitions for abnormal that I've seen before include "Deviant or unnatural" , "Highly unusual" , "Quite unusual" , "The reverse of 32 Across" , "Irregular" .)

I've seen this clue in The Sun.

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