Rider with nicer pants -- it's the latest fashion (7,3)

I believe the answer is:

dernier cri

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'the latest fashion' is the definition.
The definition suggests a singular noun which matches the answer.

'rider with nicer pants' is the wordplay.
'with' means one lot of letters go next to another.
'pants' indicates anagramming the letters (UK informal term for 'nonsense' or 'rubbish').
'rider'+'nicer'='ridernicer'
'ridernicer' is an anagram of 'DERNIER CRI'.

'it's' acts as a link.

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(Other definitions for dernier cri that I've seen before include "The latest thing" , "The last word" , "Very fashionable" .)

I've seen this clue in The Telegraph.

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