There are no words that are 6 lettered and start with a X
Then you should start to play Scrabble. These are all allowed and do have meanings in the Oxford English Dictionary.
XEBECS, XENIAL, XENIAS, XENONS, XYLANS, XYLEMS, XYLENE, XYLOID, XYLOLS, XYLOSE, XYLYLS, XYSTER, XYSTOI, XYSTOS, and XYSTUS.
borax, relax, index, ..
annex, addax
xerox
X-rays
xuse
Five letter words starting with C and ending with X are calyx and codex.
Flax.
cortex
A four letter word beginning with C and ending with X is crux.
Extra
phoenix?
Extra is a five letter word for surplus. E X T R A.
relax remex remix fedex addax admix affix annex inbox codex latex infix
Five letter words with second letter x are:excelexertextraaxiomexpel
epoxy
Pheonix
The word faux has a silent x, pronounced [foh].