Border of higher mathematics (3)
I believe the answer is:
hem
'border' is the definition.
(I've seen this before)
'of higher mathematics' is the wordplay.
'of' indicates a hidden word.
'HEM' is hidden within 'higher mathematics'.
(Other definitions for hem that I've seen before include "Border; fringe" , "Bottom of a garment" , "Double-backed border of a garment" , "may attract attention" , "It draws attention to" .)