Postgraduate gets a thousand for nocturnal insect that was extremely large (7)
I believe the answer is:
mammoth
'extremely large' is the definition.
'mammoth' can be an answer for 'large' (similar in meaning). I'm unsure of the 'extremely' bit.
'postgraduate gets a thousand for nocturnal insect' is the wordplay.
'postgraduate' becomes 'ma' (Master of Arts is a postgraduate degree).
'gets' is a charade indicator (letters next to each other).
'a thousand' becomes 'M' (Roman numeral for a thousand).
'for' is a charade indicator (letters next to each other).
'nocturnal insect' becomes 'moth' (I've seen this before).
'ma'+'m'+'moth'='MAMMOTH'
'that was' acts as a link.
Can you help me to learn more?
(Other definitions for mammoth that I've seen before include "Prehistoric woolly elephant" , "Extinct woolly creature" , "Extinct species of elephant" , "Large 15 animal" , "Enormous" .)