/usr/include/ClearSilver/ is in clearsilver-dev 0.10.5-1.6build1.
This file is owned by root:root, with mode 0o755.
..
/usr/include/ClearSilver/ClearSilver.h
/usr/include/ClearSilver/cgi/
/usr/include/ClearSilver/cgi/cgi.h
/usr/include/ClearSilver/cgi/cgiwrap.h
/usr/include/ClearSilver/cgi/date.h
/usr/include/ClearSilver/cgi/html.h
/usr/include/ClearSilver/cs/
/usr/include/ClearSilver/cs/cs.h
/usr/include/ClearSilver/cs_config.h
/usr/include/ClearSilver/util/
/usr/include/ClearSilver/util/dict.h
/usr/include/ClearSilver/util/filter.h
/usr/include/ClearSilver/util/neo_date.h
/usr/include/ClearSilver/util/neo_err.h
/usr/include/ClearSilver/util/neo_files.h
/usr/include/ClearSilver/util/neo_hash.h
/usr/include/ClearSilver/util/neo_hdf.h
/usr/include/ClearSilver/util/neo_misc.h
/usr/include/ClearSilver/util/neo_net.h
/usr/include/ClearSilver/util/neo_rand.h
/usr/include/ClearSilver/util/neo_server.h
/usr/include/ClearSilver/util/neo_str.h
/usr/include/ClearSilver/util/rcfs.h
/usr/include/ClearSilver/util/skiplist.h
/usr/include/ClearSilver/util/ulist.h
/usr/include/ClearSilver/util/ulocks.h
/usr/include/ClearSilver/util/wildmat.h