School cricket side hosted by old king (7)
I believe the answer is:
college
'school' is the definition.
(college is a kind of school)
'cricket side hosted by old king' is the wordplay.
'cricket side' becomes 'leg' (I've seen this before).
'hosted by' means one lot of letters goes inside another.
'old king' becomes 'cole'.
'leg' inserted into 'cole' is 'COLLEGE'.
(Other definitions for college that I've seen before include "Place of higher education" , "School" , "Place of learning" , "SECOND PART OF 20" , "pudding?" .)