Structural weakness of fairly big tin potty (12)

I believe the answer is:

frangibility

'structural weakness' is the definition.

'fairly big tin potty' is the wordplay.
'potty' indicates anagramming the letters.
'fairly'+'big'+'tin'='fairlybigtin'
'fairlybigtin' anagrammed gives 'FRANGIBILITY'.

'of' is the link.

I've seen this clue in The Guardian.

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