Letter stroke (5)
I believe the answer is:
serif
'letter stroke' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for serif that I've seen before include "Style of type-face" , "Short line at the end of the main stroke of a letter" , "One feature of text" , "Part of letter" , "Projection at a letter's end" .)