Material uni students gathered during half-term (5)
I believe the answer is:
tulle
'material' is the definition.
(tulle is a kind of material)
I cannot understand how the rest of the clue works.
(Other definitions for tulle that I've seen before include "Fine netting used for veils" , "Delicate silk fabric" , "Delicate netted fabric" , "Fine net fabric used for evening dresses" , "Material used for veils" .)