Clue: All-round experts in HE establishment no longer having single academic discipline (9)
Answer: POLYMATHS
Explanation: Definition: All-round experts
A charade of POLY ( 'HE establishment no longer' – Higher Education, that is, not High Explosive) plus MATHS ('single academic discipline'). I am not quite sure what 'single' is doing there, unless it is just to indicate the apparent plural of MATHS (in the US math is the common abbreviation).