Education centre supported by variable software system (4)
I believe the answer is:
unix
'software system' is the definition.
(UNIX is an example)
'education centre supported by variable' is the wordplay.
'education centre' becomes 'uni'.
'supported by' is a charade indicator (letters next to each other) (in a down clue, some letters hold up others).
'variable' becomes 'x' (x may represent a variable in algebra).
'uni'+'x'='UNIX'
(Other definitions for unix that I've seen before include "See this operating system" , "Computer open operating system" , "software" .)