Son in peace mad to break free (6)
I believe the answer is:
escape
'break free' is the definition.
(I've seen this in another clue)
'son in peace mad' is the wordplay.
'son' becomes 's' (genealogical abbreviation for son).
'in' means one lot of letters goes inside another.
'mad' indicates an anagram.
'peace' anagrammed gives 'ecape'.
's' put within 'ecape' is 'ESCAPE'.
'to' is the link.
(Other definitions for escape that I've seen before include "has to fly" , "bolt" , "Manage to avoid" , "Elude; leakage" , "find way out" .)