/usr/lib/x86_64-linux-gnu/libtcl.a is in tcl-dev 8.6.0+8.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libtcl8.6.a
/usr/lib/x86_64-linux-gnu/libtcl8.6.a