Uproar during exam leads to third for one (7)
I believe the answer is:
ordinal
'third for one' is the definition.
(third is an example)
'uproar during exam' is the wordplay.
'uproar' becomes 'din' (I've seen this in other clues).
'during' is an insertion indicator.
'exam' becomes 'oral' (oral exam is a kind of exam).
'din' placed into 'oral' is 'ORDINAL'.
'leads to' is the link.
(Other definitions for ordinal that I've seen before include "Roman Catholic service book" , "First, second, third etc." , "Relating to position in a sequence" , "Eg second" , "First, second, third could be such a numeral" .)