Listening intently, a student attached to King's (3,4)
I believe the answer is:
all ears
'listening intently' is the definition.
(I've seen this before)
'a student attached to king's' is the wordplay.
'student' becomes 'l'.
'attached to' means one lot of letters go next to another.
'king's' becomes 'lears' (**).
'a'+'l'+'lears'='ALL EARS'
(Other definitions for all ears that I've seen before include "Being very attentive" , "Very alert" , "Listening attentively" , "description of cornfield?" , ".Listening very intently" .)