I break bail in order to prove I was elsewhere (5)
I believe the answer is:
alibi
'to prove i was elsewhere' is the definition.
'i break bail in order' is the wordplay.
'break' means one lot of letters goes inside another (inserted letters break into the word).
'in order' indicates an anagram (the letters in a new order).
'bail' with letters rearranged gives 'albi'.
'i' going into 'albi' is 'ALIBI'.
(Other definitions for alibi that I've seen before include "Courtroom evidence" , ""suspect's story"" , "Excuse - plea of being elsewhere" , "Legal defence, plea" , "in order to prove I was elsewhere" .)