Fails to enter river cooler or hotter than others (9)

I believe the answer is:

trendiest

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'cooler or hotter than others' is the definition.
I can't judge whether this defines the answer.

'fails to enter river' is the wordplay.
'fails' becomes 'dies' ('die' can be a synonym of 'fail').
'to enter' indicates putting letters inside.
'river' becomes 'trent' (River Trent).
'dies' put into 'trent' is 'TRENDIEST'.

Can you help me to learn more?

(Other definitions for trendiest that I've seen before include "cooler than the rest" , "Most cool!" , "Most popular" .)

I've seen this clue in The Independent.

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