Magistrate is about right to snap (5)
I believe the answer is:
break
'snap' is the definition.
(I've seen this before)
'magistrate is about right' is the wordplay.
'magistrate' becomes 'beak' (informal term).
'is about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'beak' enclosing 'r' is 'BREAK'.
'to' acts as a link.
(Other definitions for break that I've seen before include "Interrupt - rest period" , "Shatter; interval" , "Holiday - destroy" , "Holiday; decipher (code)" , "Fracture; holiday" .)