Peacekeepers and police force not satisfied (5)
I believe the answer is:
unmet
'not satisfied' is the definition.
(I've seen this in another clue)
'peacekeepers and police force' is the wordplay.
'peacekeepers' becomes 'UN' (United Nations, peacekeeping organisation).
'and' means one lot of letters go next to another.
'police force' becomes 'met' (short for Metropolitan Police Service).
'un'+'met'='UNMET'
(Other definitions for unmet that I've seen before include "(Of requirement) not fulfilled" , "not achieved" , "Not satisfied with" , "Outstanding" .)