Big lizard droppings collected by one academic (9)
I believe the answer is:
iguanodon
'big lizard' is the definition.
'iguanodon' can be an answer for 'lizard' (I have seen 'Old lizard' mean 'iguanodon' so perhaps 'lizard' could also mean 'iguanodon'). I am not sure about the 'big' bit.
'droppings collected by one academic' is the wordplay.
'droppings' becomes 'guano' (term for bird droppings).
'collected by' is a charade indicator (letters next to each other) (I've seen this in other clues).
'one' becomes 'i' (Roman numeral).
'academic' becomes 'don' (type of academic - especially at Oxbridge).
'guano' put after 'i' is 'iguano'.
'iguano'+'don'='IGUANODON'
Can you help me to learn more?
(Other definitions for iguanodon that I've seen before include "Herbivorous dinosaur" , "Massive dinosaur of the early Cretaceous period" , "big beast" , "Large dinosaur" , "Massive dinosaur with long heavy tail" .)