Head boy securing a point (4)
I believe the answer is:
lead
'head' is the definition.
('lead' can be a synonym of 'head')
'boy securing a point' is the wordplay.
'boy' becomes 'lad' (lad is a kind of boy**).
'securing' is an insertion indicator.
'a point' becomes 'e' (E is an example).
'lad' placed around 'e' is 'LEAD'.
(Other definitions for lead that I've seen before include "Guide by going in front" , "First news item" , "Principal role in a play" , "First put down spade, say" , "Take the van with heavy metal" .)