### Clue: Regular features in column disheartened colleague having little weight (5)
### Answer: OUNCE 
 ### Explanation: Definition: little weight
  OUN{second, fourth and sixth letters(regular features) in "column"} + CE{"colleague" **minus** its inner letters(disheartened,heart extracted)}. 
Answer: You might be too young to have had to learn in school "16 ozs make a lb weight, 14 lbs make a stone, 112 lbs make a cwt, and 20 cwts make a ton" pre-metrication.  As I memorised them, I often wondered, "Where did those diaboloical numbers come from?"