First for group closing, performing cover for festival (11)
I believe the answer is:
glastonbury
'for festival' is the definition.
(UK music festival)
'first for group closing performing cover' is the wordplay.
I cannot really understand how this works, but
'first' could be 'a' (first letter of the alphabet) and 'a' is located in the answer.
'for' could be 'to' (eg both can mean 'in the opinion of') and 'to' is present in the answer.
'cover' could be 'bur' (bur is a kind of cover) and 'bur' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for glastonbury that I've seen before include "Somerset pop festival" , "Somerset music festival" , "where pop festival's held" , "Festival venue in Somerset" , "festival site" .)