Ditch has to be found in county (6)
I believe the answer is:
disown
'ditch' is the definition.
(to disown is to ditch or abandon)
'has to be found in county' is the wordplay.
'has to be' becomes 'is' ('he's fair' could mean 'he has to be fair').
'found in' means one lot of letters goes inside another.
'county' becomes 'down' (County Down in Northern Ireland).
'is' inserted into 'down' is 'DISOWN'.
(Other definitions for disown that I've seen before include "Disclaim or deny" , "Repudiate, cast off" , "Reject all connection with, refuse to acknowledge" , "Repudiate or refuse to acknowledge a relationship" , "Cast aside" .)