gprclean: 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 Debian possible default full paths are:

/usr/bin/gprclean - from package: gprbuild

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

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