The most common and most likely answer to this crossword clue is the 9 plus 6 letter word RADCLIFFE CAMERA
I've seen this crossword clue in The Daily Telegraph
R
A
D
C
L
I
F
F
E
C
A
M
E
R
A
More clues leading to the result RADCLIFFE CAMERA
Buddy explains!

The straight part
We know that "famous university building" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case famous university building = radcliffe camera.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.