Very unpleasant mob shortly around Rhode Island (6)
I believe the answer is:
horrid
'very unpleasant' is the definition.
(I've seen this before)
'mob shortly around rhode island' is the wordplay.
'mob' becomes 'horde' (horde can mean a mob or crowd of people).
'shortly' means to remove the last letter.
'around' indicates putting letters inside.
'rhode island' becomes 'RI' (US postal abbreviation).
'horde' with its final letter taken off is 'hord'.
'hord' placed around 'ri' is 'HORRID'.
(Other definitions for horrid that I've seen before include "Nasty, frightening" , "Appalling" , "Dreadful" , "Unpleasant, not nice" , "Repellent" .)