Would you mind sharing what that alias would look like and do? I can only imagine it appending the string "| tmenu" to the current line, eventually pressing Return for the user as well.
Warning: seems like GNU readline isn't case sensitive so C-L === C-l thus, in this example, C-l default behavior (clear screen?) is overridden. I didn't RTFM so trust yourself.
ps: I'd add a readline/inputrc alias for '| tmenu '