Boy should go to an HE establishment? There's agreement (6)
I believe the answer is:
unison
'there's agreement' is the definition.
(I've seen this before)
'boy should go to an he establishment?' is the wordplay.
'boy' becomes 'son' (synonyms).
'should go to' says to put letters next to each other.
'an he establishment?' becomes 'uni' (university - higher education establishment).
'son' after 'uni' is 'UNISON'.
(Other definitions for unison that I've seen before include "All acting the same way at the same time" , "Sameness in pitch" , "Public service trade union" , "concert" , "Complete agreement, harmony" .)