Schoolboy traps the compiler set! (4)
I believe the answer is:
laid
'set' is the definition.
(synonyms)
'schoolboy traps the compiler' is the wordplay.
'schoolboy' becomes 'lad' (lad can mean a young boy).
'traps' means one lot of letters goes inside another.
'the compiler' becomes 'i' (the person who is writing these clues).
'lad' placed around 'i' is 'LAID'.
(Other definitions for laid that I've seen before include "Prepared (a trap)" , "Doze" , "Deposited" , "spread on a surface" , "settled" .)