Tie up that mess overshadowing a college (6)
I believe the answer is:
attach
'tie' is the definition.
(attaching is a kind of tiing)
'up that mess overshadowing a college' is the wordplay.
I cannot quite understand how this works, but
'a' is within the answer.
'college' could be 'c' and 'c' is found within the answer.
an anagram of 'that' is 'ttah' which is present in the left over letters.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for attach that I've seen before include "Add to, connect" , "Affix, connect" , "Append, join" , "Unite?" , "Secure" .)