A knotty old dear (6)
I believe the answer is:
granny
'old dear' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
'a knotty' is the wordplay.
I cannot quite understand how this works, but
'a' could be 'an' and 'an' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for granny that I've seen before include "Family relative" , "Female relative" , "Sort of knot" , "Insecure knot" , "Old woman" .)