Slim fit of pants not to be discussed (3-6)

I believe the answer is:

off-limits

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'not to be discussed' is the definition.
I can't tell whether this definition defines the answer.

'slim fit of pants' is the wordplay.
'pants' indicates an anagram (UK informal term for 'nonsense' or 'rubbish').
'slim'+'fit'+'of'='slimfitof'
'slimfitof' with letters rearranged gives 'OFF-LIMITS'.

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(Other definitions for off-limits that I've seen before include "Out of bounds" , "Restricted" .)

I've seen this clue in The Telegraph.

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