Core of county police force not satisfied (5)
I believe the answer is:
unmet
'not satisfied' is the definition.
(I've seen this in another clue)
'core of county police force' is the wordplay.
'core of' means to look at the middle letters.
'police force' becomes 'met' (short for Metropolitan Police Service).
The central letters of 'county' are 'un'.
'un'+'met'='UNMET'
(Other definitions for unmet that I've seen before include "Not satisfied with" , "not achieved" , "Outstanding" , "(Of requirement) not fulfilled" .)