Setback concerning Northern Europeans by the sound of it (7)
I believe the answer is:
relapse
'setback' is the definition.
(I've seen this before)
'concerning northern europeans by the sound of it' is the wordplay.
'concerning' becomes 're' (both can mean on a particular topic).
'northern europeans' becomes 'Lapps' (people from Lapland).
'by the sound of it' indicates a 'sounds like' (homophone) clue.
'lapps' is a homophone of 'lapse'.
're'+'lapse'='RELAPSE'
(Other definitions for relapse that I've seen before include "go back" , "Sink back into illness" , "Return to sickness" , "Backslide as in health matters" , "Get into bad habits again" .)