Massive dinosaur droppings gathered by one college fellow (9)
I believe the answer is:
iguanodon
'massive dinosaur' is the definition.
'iguanodon' can be an answer for 'dinosaur' (iguanodon is a kind of dinosaur). I'm not certain of the 'massive' bit.
'droppings gathered by one college fellow' is the wordplay.
I cannot really understand how this works, but
'droppings' could be 'guano' (term for bird droppings) and 'guano' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'fellow' could be 'don' (both can mean an academic) and 'don' is present in the answer.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for iguanodon that I've seen before include "fossil" , "Herbivorous dinosaur" , "It used to eat plants" , "big beast" , "reptile now extinct" .)