Tiny creature displayed in American university by top educator (4)
I believe the answer is:
mite
'tiny creature' is the definition.
(I've seen this in another clue)
'american university by top educator' is the wordplay.
'american university' becomes 'mit' (Massachusetts Institute of Technology).
'by' is a charade indicator (letters next to each other).
'top' indicates taking the first letters (in a down clue, the first letter is top).
The first letter of 'educator' is 'e'.
'mit'+'e'='MITE'
'displayed in' is the link.
(Other definitions for mite that I've seen before include "Very small creature or child" , "Child; a small amount" , "The Biblical widow's offering" , "The widow's small offering" , "Old piece" .)