Make up with non-commissioned officer in county court (7)
I believe the answer is:
concoct
'make up' is the definition.
(concocting is a kind of making up)
'non-commissioned officer in county court' is the wordplay.
'non commissioned officer' becomes 'NCO' (abbreviation).
'in' means one lot of letters goes inside another.
'county' becomes 'co'.
'court' becomes 'ct' (abbreviation used in road names).
'co'+'ct'='coct'
'nco' placed inside 'coct' is 'CONCOCT'.
'with' is the link.
(Other definitions for concoct that I've seen before include "Fabricate" , "cook" , "Invent, devise" , "Invent (a story)" , "Invent (a story/plan)" .)