Pedant demands that one covers every iota! (6)
I believe the answer is:
tittle
'iota' is the definition.
(I know that iota can be written as tittle)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for tittle that I've seen before include "A printed dot as in i" , "Smallest part (after a jot?)" , "Companion to jot" , "Tiny printed mark" , "A tiny bit" .)