svn-clean: command not found

Maybe Your $PATH variable doesn't contain the default paths? echo $PATH should give something like:

[root@server ~]# echo $PATH
/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin

If it's empty, You may set the PATH variable with this command

export PATH="/usr/local/sbin:/usr/local/bin:/sbin:/bin:/usr/sbin:/usr/bin:/root/bin"

On CentOS possible default full paths are:

/usr/bin/svn-clean - from package: kdesdk

You may install the required package with command yum install {package}

On Debian possible default full paths are:

/usr/bin/svn-clean - from package: subversion-tools

You may install the required package with command apt-get install {package}

Error in other languages:
svn-clean: bevel nie gevind nie
svn-clean: comandă negăsită
svn-clean: comando não encontrado
svn-clean: commande introuvable
svn-clean: command not found
svn-clean: käsku ei ole
svn-clean: không tìm thấy lệnh
svn-clean: komanda nerasta
svn-clean: Kommando nicht gefunden.
svn-clean: kommandot finns inte
svn-clean: komut yok
svn-clean: nie znaleziono polecenia
svn-clean: níor aimsíodh an t-ordú
svn-clean: no se encontró la orden
svn-clean: no s'ha trobat l'ordre
svn-clean: opdracht niet gevonden
svn-clean: parancs nem található
svn-clean: perintah tidak ditemukan
svn-clean: príkaz nenájdený
svn-clean: příkaz nenalezen
svn-clean: команда не найдена
svn-clean: командата не е открита
svn-clean: 命令找不到
svn-clean: コマンドが見つかりません