Rarely on time, you held policeman up (7)
I believe the answer is:
mountie
'policeman up' is the definition.
(Canadian policeman up on a horse)
'rarely on time you held' is the wordplay.
'rarely' indicates an anagram (rare can mean unusual or strange).
'you' becomes 'u' (commonly used in online communication).
'held' indicates putting letters inside.
'on'+'time'='ontime'
'ontime' is an anagram of 'montie'.
'montie' enclosing 'u' is 'MOUNTIE'.
(Other definitions for mountie that I've seen before include "Canadian policeman" , "One boasting of getting man" , "Canadian police officer" , "Canadian policemen" , "Horse-riding Canadian cop" .)