Concert, issue of educational institution? (6)
I believe the answer is:
unison
'concert' is the definition.
(to work in concert is to work in unison)
'issue of educational institution?' is the wordplay.
I cannot quite see how this works, but
'issue' could be 'son' (issue can mean someone's offspring) and 'son' is present in the answer.
'educational institution?' could be 'uni' (short for university) and 'uni' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for unison that I've seen before include "Sameness in pitch" , "Type of singing" , "concert" , "All voices together" , "All singing the same notes" .)