Clue: Laughed at reading 1 down — setter had put in funny clue (9)
Answer: RIDICULED
Explanation: Definition: Laughed at 
 R(abbrev. for "reading", from the "three Rs of children's education") + I(Roman numeral for "one") + D(abbrev. for "down", as with, say, crossword clues) + I'D("I had"/setter had, using the self-referential pronoun) **containing**(put in) **anagram of**(funny) CLUE.