Clue: Capers in mains, oddly, yours truly fed to cook (8)
Answer: MISCHIEF
Explanation: Definition: Capers
 **1st, 3rd and 5th letters of**(…, oddly) "mains" + [ I(yours truly, the setter using the self-referential pronoun) **contained in**(fed to) CHEF(a professional cook) ].