King finds no students at mound (5)
I believe the answer is:
knoll
'mound' is the definition.
('knoll' can be a synonym of 'mound')
'king finds no students' is the wordplay.
'king' becomes 'k'.
'finds' means one lot of letters go next to another.
'students' becomes 'll'.
'k'+'no'+'ll'='KNOLL'
'at' acts as a link.
(Other definitions for knoll that I've seen before include "Little mound" , "minor eminence" , "Hummock" , "Little hill" , "Small round hill" .)