Weight formerly revealed outside university (5)
I believe the answer is:
ounce
'weight' is the definition.
(unit of weight)
'formerly revealed outside university' is the wordplay.
I cannot really understand how this works, but
'university' could be 'ou' and 'ou' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for ounce that I've seen before include "Small imperial weight" , "16 for a pound" , "Unit equal to about 28 grams" , "One sixteenth of a pound" , "Large cat" .)