Knot for elderly relative (6)
I believe the answer is:
granny
This could be a double definition.
'knot' is the first definition.
(granny knot is a kind of knot)
'elderly relative' is the second definition.
'granny' can be an answer for 'relative' (granny is a kind of relative). I'm unsure of the 'elderly' bit.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for granny that I've seen before include "Nan" , "Insecure knot" , "(Knotty?) relative" , "A parent's mother" , "Relative and type of knot" .)