She's related in a small way (3)
I believe the answer is:
sis
'she's' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's an association between them I don't understand?
'related in a small way' is the wordplay.
'related' becomes 'i' (I can't explain this - if you can you should believe this answer much more).
'in' indicates putting letters inside.
'a small' becomes 's' (abbreviation - e.g. clothes size).
'way' becomes 's' (Compass direction - South).
's'+'s'='ss'
'i' going within 'ss' is 'SIS'.
Can you help me to learn more?
(Other definitions for sis that I've seen before include "Secret Intelligence Service (abbreviation)" , "Family member (informal)" , "Relative's" , "Sibling (informal)" , "Girl" .)