A small tick (6)
I believe the answer is:
minute
I believe this is a double definition.
'a small' is the first definition.
(I've seen this before)
'tick' is the second definition.
(thesaurus)
(Other definitions for minute that I've seen before include "Exact" , "Very small; record" , "Brief note" , "barely noticeable?" , "Tiny like time unit (6)" .)