Leading university finds odd series of mysterious things (4)
I believe the answer is:
ufos
'mysterious things' is the definition.
(I've seen this before)
'leading university finds odd series' is the wordplay.
'leading' says to take the initial letters (the leading letter of the word).
The initial letters of 'university finds odd series' is 'UFOS'.
'of' is the link.
(Other definitions for ufos that I've seen before include "Initially, official flying saucers" , "Supposed alien craft" , "Mysterious phenomena" , "Supposed spaceships" , "Mysterious objects in sky" .)