Eccentric, like policeman who has finished duty? (7)
I believe the answer is:
offbeat
I believe this is a double definition.
'eccentric' is the first definition.
(thesaurus)
'like policeman who has finished duty?' is the second definition.
(a policeman's shift may be called his 'beat')
(Other definitions for offbeat that I've seen before include "Unconventional or lacking rhythm" , "Quirky" , "Odd, unconventional" , "Strange" , "Unusual, not ordinary - or rhythmic" .)