Extremely small or long hand (6)
I believe the answer is:
minute
This clue could be a double definition.
'extremely small' is the first definition.
(I've seen this before)
'long hand' is the second definition.
'minute' can be an answer for 'hand' (thesaurus). I'm unsure of the 'long' bit.
'or' is the link.
Can you help me to learn more?
(Other definitions for minute that I've seen before include "Brief note" , "not much time" , "Very short or tiny" , "Sixty seconds" , "barely noticeable?" .)