Melon fanatic (3)
I believe the answer is:
nut
This clue might be a double definition.
'melon' is the first definition.
The definition and answer can be both plants as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'fanatic' is the second definition.
(I've seen this in another clue)
Can you help me to learn more?
(Other definitions for nut that I've seen before include "keen admirer" , "Enthusiast (slang)" , "Fruitcake" , "eg Pecan" , "Almond, for example" .)