tcsh shortcut to move the cursor back to previous space

If you mean keyboard shortcut at the prompt of interactive bash shells, you could bind the shell-backward-word and shell-forward-word to some sequence of characters sent upon some key or combination of key presses.

Like if pressing Ctrl-Left sends the sequence \e[1;5D on your terminal like it does in xterm, you could do:

bind '"\e[1;5D": shell-backward-word'
bind '"\e[1;5D": shell-backward-word'

Note that it does not jump from blank to blank but considers shell quoting. So for instance in a line like

echo "foo 'bar baz' blah/bleh bloh
^   ^              ^         ^

It would jump to the locations marked above.

Edit: for tcsh, you have three options:

1. Use the equivalent to the bash definition above, either in ~/.cshrc or in /etc/csh.cshrc.local to give all users the benefit.

   bindkey '\e[1;5D' backward-word
   bindkey '\e[1;5C' forward-word
   

2. Use the vi mode (with bindkey -v) and use the B and W keys in normal mode just like in vi.

3. In emacs mode (the default, reenabled with bindkey -e) like for bash, bind the corresponding widgets (vi-word-back and vi-word-fwd):

   bindkey '\e[1;5C' vi-word-fwd
   bindkey '\e[1;5D' vi-word-back
   

Note that those are like vi's B and W, so they're for jumping between blank separated words, not shell tokens (like quoted strings) like in the bash solution above.