Upsetting cur, Vera's wart (7)
I believe the answer is:
verruca
'wart' is the definition.
(I know that verruca is a type of wart)
'upsetting cur vera's' is the wordplay.
'upsetting' indicates anagramming the letters.
'cur'+'vera'='curvera'
'curvera' anagrammed gives 'VERRUCA'.
(Other definitions for verruca that I've seen before include "Wart on the sole of the foot" , "Wartlike growth often on foot" , "1 across" , "Wart-like swelling on the foot" , "Kind of wart of foot" .)