Capers in mains, oddly, yours truly fed to cook (8)
I believe the answer is:
mischief
'capers' is the definition.
(capers are mischievous schemes)
'mains oddly yours truly fed to cook' is the wordplay.
'oddly' indicates alternate letters (letters in the odd-numbered positions are used).
'yours truly' becomes 'I' (the person that set this crossword).
'fed to' indicates putting letters inside.
'cook' becomes 'chef' (both can mean someone who cooks).
The alternate letters of 'mains' are 'mis'.
'i' put inside 'chef' is 'chief'.
'mis'+'chief'='MISCHIEF'
'in' is the link.
(Other definitions for mischief that I've seen before include "Playful troublemaking" , "Devilment, roguishness" , "Devilment, impishness" , "(Playfully) destructive behaviour" , "Reckless behaviour" .)