### Clue: Relative monstrosity is carbohydrate-free (5)
### Answer: UNCLE 
 ### Explanation: Definition: Relative
  Carbuncle(a skin eruption, larger than a boil, caused by a staphylococcal(staph) infection, would look like a *monstrosity* in an extreme case)  without(*free*) of carb(short for *carbohydrate*).  (No graphics in deference to the squeamish.)