Rugby boss perhaps understanding control (10)
I believe the answer is:
headmaster
'rugby boss perhaps' is the definition.
(Rugby is an English private school)
'understanding control' is the wordplay.
'understanding' becomes 'head' (eg a head for figures is an understanding of them).
'control' becomes 'master' (mastering is a kind of controlling).
'head'+'master'='HEADMASTER'
(Other definitions for headmaster that I've seen before include "Top (male) teacher" , "Principal" , "School manager" .)