\define\ItemCommand
    {\hskip\zeropoint\relax\autoinsertnextspace}

  \setupitemgroup
    [itemize]
    [color=darkred,
style=bold,
     distance=\spaceamount]

  \setupitemgroup
    [itemize:1]
    [option={n,packed,fit,intext},
    command=\ItemCommand]

  \setupitemgroup
    [itemize:2]
    [lefttext=,
    righttext=,
    option={a,text}]

\setupenumerations
  [before={},
   after={\blank},
   alternative=serried,
   number=no,
   title=yes,
   titleleft={(},
   titleright={)},
   prefix=yes,
   prefixsegments=chapter,
   way=bychapter,
   titlestyle=bold,
   width=broad]

\defineenumeration
   [definition]
   [text=Définition,
    number=no,
    headcommand=\groupedcommand{}{},
    style=normal]

\starttext
\startdefinition
  \input knuth
\stopdefinition
\startdefinition
  \startitemize[n]
    \startitem
      First item
    \stopitem
    \startitem
      Second item
    \stopitem
  \stopitemize
\stopdefinition
\stoptext