Best fool led by Open University (6)
I believe the answer is:
outwit
'best' is the definition.
(thesaurus)
'fool led by open university' is the wordplay.
'fool' becomes 'twit' (both can mean a stupid person).
'led by' means one lot of letters go next to another (some letters go in front of others).
'open university' becomes 'OU'.
'twit' put after 'ou' is 'OUTWIT'.
(Other definitions for outwit that I've seen before include "Get the better of by being smarter" , "Hoodwink" , "Get the better of by cunning" , "Deceive through greater ingenuity" , "Intellectually get the better of" .)