Let in again to study at Massachusetts university (7)
I believe the answer is:
readmit
'let in again' is the definition.
('admit' can be a synonym for 'let in' so perhaps 'readmit' is OK for 'let in again')
'study at massachusetts university' is the wordplay.
'study' becomes 'read' (synonyms).
'at' says to put letters next to each other.
'massachusetts university' becomes 'mit' (I can't explain this - if you can you should give a lot more credence to this answer).
'read'+'mit'='READMIT'
'to' is the link.
Can you help me to learn more?
(Other definitions for readmit that I've seen before include "Let in a second time" , "Allow back into" , "Let back in" , "Dear Tim (anag.)" , "Take in again" .)