A growing attachment (7)
I believe the answer is:
tendril
'a growing attachment' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
This is all the clue.
Can you help me to learn more?
(Other definitions for tendril that I've seen before include "Slender structure on some twining plants" , "Gripping part of climbing plant" , "Twisted lock of hair" , "Part of twining plant" , "Plant's climbing aid" .)