Falls in river with utmost style (9)
I believe the answer is:
trendiest
'falls in river with utmost style' is the definition.
I can't judge whether this defines the answer.
'river with utmost style' is the wordplay.
'river' becomes 'trent' (River Trent).
'with' indicates putting letters inside.
'utmost style' becomes 'dies' (I can't explain this - if you can you should give a lot more credence to this answer).
'trent' going around 'dies' is 'TRENDIEST'.
Can you help me to learn more?
(Other definitions for trendiest that I've seen before include "Most popular" , "cooler than the rest" , "Most cool!" .)