Concern about to be presented in paper (4)
I believe the answer is:
fret
'concern' is the definition.
(thesaurus)
'about to be presented in paper' is the wordplay.
'about' becomes 're' (regarding**).
'to be presented in' means one lot of letters goes inside another.
'paper' becomes 'ft'.
're' placed inside 'ft' is 'FRET'.
(Other definitions for fret that I've seen before include "Part of a Gibson, say" , "Worry; or the marking on a guitar" , "Vex oneself - part of a fingerboard" , "coastal mist" , "Split up" .)