Oppressive individual with sour disposition (7)
I believe the answer is:
onerous
'oppressive' is the definition.
(onerous can mean crushing or oppressive)
'individual with sour disposition' is the wordplay.
'individual' becomes 'one' (an individual is one person).
'with' means one lot of letters go next to another.
'disposition' indicates an anagram.
'sour' anagrammed gives 'rous'.
'one'+'rous'='ONEROUS'
(Other definitions for onerous that I've seen before include "Involving much work" , "No euros? That's burdensome" , "Difficult, troublesome" , "Burdensome, taxing" , "quite a burden if so" .)