Dealing with jazz in Gateshead (7)
I believe the answer is:
trading
'dealing' is the definition.
(I've seen this before)
'with jazz in gateshead' is the wordplay.
'with' says to put letters next to each other.
'jazz' becomes 'trad' (trad jazz is a type of jazz).
'gateshead' becomes 'g' (head letter of 'gates').
'trad' put next to 'in' is 'tradin'.
'tradin'+'g'='TRADING'
(Other definitions for trading that I've seen before include "In business" , "Commercial activity" , "in the marketplace" , "Buying and selling" , "Dealing" .)