Clue: Straight used car improperly disposed of from converted terraced house (6)
Answer: HETERO
Explanation: Definition: Straight
Anagram of TERRACED HOUSE less USED CAR – subtractive anagrams like this are common in Otterden's puzzles. There are two anagram indicators ("improperly" and "converted") to show that the removed letters are not in the same order in the main fodder. Some people care a lot about this, but I am not among them – it seems to me that you can shuffle TERRACED HOUSE to get HETERO USED CAR, and then remove USED CAR.