Changing pants idea is so cool (13)

I believe the answer is:

dispassionate

'cool' is the definition.
(thesaurus)

'changing pants idea is so' is the wordplay.
'changing' indicates anagramming the letters.
'pants'+'idea'+'is'+'so'='pantsideaisso'
'pantsideaisso' is an anagram of 'DISPASSIONATE'.

(Other definitions for dispassionate that I've seen before include "Imperturbable" , "Not affected by personal feelings" , "Rational, impartial" , "Objective, unemotional" , "taking the unbiased view?" .)

I've seen this clue in The Times.

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