Second marine upset with year in college (8)
I believe the answer is:
seminary
'college' is the definition.
(college for priests)
'second marine upset with year' is the wordplay.
'second' becomes 's' (common abbreviation).
'upset with' is an anagram indicator.
'year' becomes 'y'.
'marine' with its letters mixed up with 'y' makes 'eminary'.
's'+'eminary'='SEMINARY'
'in' is the link.
(Other definitions for seminary that I've seen before include "School for clerics" , "College for trainee priests" , "Theological school" , "Theological college" , "School for priests" .)