Giant animal droppings make nitrogen beneath one (9)
I believe the answer is:
iguanodon
'giant animal' is the definition.
The answer and definition can be both animals as well as being singular nouns.
Perhaps there's an association between them I don't understand?
'droppings make nitrogen beneath one' is the wordplay.
'droppings' becomes 'guano' (term for bird droppings).
'make' becomes 'do' (do can mean to make or prepare).
'nitrogen' becomes 'N' (N is the chemical symbol for nitrogen).
'beneath' is a charade indicator (letters next to each other) (in a down clue, some letters go beneath others).
'one' becomes 'i' (Roman numeral).
'guano'+'do'+'n'='guanodon'
'guanodon' put after 'i' is 'IGUANODON'.
Can you help me to learn more?
(Other definitions for iguanodon that I've seen before include "In the past a massive herbivore" , "Massive dinosaur of the early Cretaceous period" , "Massive dinosaur with long heavy tail" , "Long-tailed bipedal dinosaur" , "Large dinosaur" .)