One new exam in English of which colon is a part (9)
I believe the answer is:
intestine
'a part' is the definition.
(intestine is a kind of part)
'one new exam in english' is the wordplay.
'one' becomes 'i' (Roman numeral).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'exam' becomes 'test' (synonyms).
'english' becomes 'E' (abbreviation).
'i'+'n'+'test'+'in'+'e'='INTESTINE'
'of which colon is' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for intestine that I've seen before include "Being gutted, one loses it" , "canal section" , "Some guts" , "Part of the alimentary canal" .)