Can understand; it is a pointer (5)
I believe the answer is:
digit
'a pointer' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'can understand it' is the wordplay.
'can understand' becomes 'dig' (I can't justify this - if you can you should believe this answer much more).
'dig'+'it'='DIGIT'
'is' is the link.
Can you help me to learn more?
(Other definitions for digit that I've seen before include "a number less than ten" , "Like It?" , "One in ten, say" , "Finger, thumb or toe" , "One's on hand" .)