PM inhales dope with Hoskins here and there in Rome (6)
I believe the answer is:
passim
'here and there in rome' is the definition.
(Latin word meaning at various places in a text)
'pm inhales dope with hoskins' is the wordplay.
'inhales' means one lot of letters goes inside another (inserted letters are inhaled).
'dope' becomes 'ass' (both can mean a stupid person).
'with' is a charade indicator (letters next to each other).
'hoskins' becomes 'I' (where the crossword setter is 'Hoskins').
'ass'+'i'='assi'
'pm' going around 'assi' is 'PASSIM'.
(Other definitions for passim that I've seen before include "Throughout (a piece of writing) - frequently cited" , "(Lit.) throughout, everywhere" , "At many points in book" , "(Of references) at various places through the text" .)