Unpleasant rumour about high honour (7)
I believe the answer is:
noisome
'unpleasant' is the definition.
(I've seen this before)
'rumour about high honour' is the wordplay.
'rumour' becomes 'noise' (I've seen this before).
'about' indicates putting letters inside.
'high honour' becomes 'OM' (Order of Merit).
'noise' placed around 'om' is 'NOISOME'.
(Other definitions for noisome that I've seen before include "Evil-smelling - sounds loud" , "Odious" , "Odorous" , "Evil-smelling, objectionable (7)" , "Foul-smelling, noxious" .)