Know boy turning up in Cumbrian town (6)
I believe the answer is:
kendal
'cumbrian town' is the definition.
(I've seen this before)
'know boy turning up' is the wordplay.
'know' becomes 'ken' (Scottish term meaning to know).
'boy' becomes 'lad' (informal term for boy).
'turning up' is a reversal indicator.
'lad' backwards is 'dal'.
'ken'+'dal'='KENDAL'
'in' is the link.
(Other definitions for kendal that I've seen before include "Town in Cumbria" , "Cumbrian town; green cloth name" , "Lakeland town known for mint cake" , "Cumbrian town - gateway to the Lake District" .)