Crossword Genius

Their own pants became threadbare (4,4)

Ross

I believe the answer is:

wore thin

'became threadbare' is the definition.
(to wear thin is to become threadbare or old)

'their own pants' is the wordplay.
'pants' indicates an anagram (UK informal term for 'nonsense' or 'rubbish').
'their'+'own'='theirown'
'theirown' is an anagram of 'WORE THIN'.

I've seen this clue in The Guardian.
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