Joined the force (3)
I believe the answer is:
met
This clue is a double definition.
'joined' is the first definition.
(meeting is a kind of joining)
'the force' is the second definition.
(I've seen this in other clues)
(Other definitions for met that I've seen before include "Got together" , "Encountered by chance or arrangement" , "Encountered pro tem" , "Came across - police in London" , "Encountered, came across" .)