Crossword Genius

Mark's trendy way of speaking including American (10)

Ross

I believe the answer is:

indication

'mark's' is the definition.
(thesaurus)

'trendy way of speaking including american' is the wordplay.
'trendy' becomes 'in' ('in' can mean fashionable).
'way of speaking' becomes 'diction' (I've seen this before).
'including' indicates putting letters inside.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'diction' going around 'a' is 'dication'.
'in'+'dication'='INDICATION'

(Other definitions for indication that I've seen before include "Sign (of something)" , "it shows" , "form of evidence" .)

I've seen this clue in The Telegraph.
Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.