Letter showing personality (9)
I believe the answer is:
character
I believe this clue is a double definition.
'letter' is the first definition.
(written character)
'personality' is the second definition.
(I've seen this before)
'showing' is the link.
(Other definitions for character that I've seen before include "Letter or number" , "strength of mind" , "I, for example" , "Personal moral qualities" , "Nature; good reputation" .)