Party contributing to our reputation (5)
I believe the answer is:
odour
'reputation' is the definition.
(odour can mean bad reputation)
'party contributing to our' is the wordplay.
'party' becomes 'do' (do can informally mean a party).
'contributing to' is an insertion indicator (inserted letters make a new contribution).
'do' placed inside 'our' is 'ODOUR'.
(Other definitions for odour that I've seen before include "Distinctive smell" , "pervasive quality" , "Smell, scent" , "Nasty smell" , "Aroma, smell" .)