Former prisoner hiding record, before it raised anomaly (9)
I believe the answer is:
exception
'anomaly' is the definition.
(thesaurus)
'former prisoner hiding record before it raised' is the wordplay.
'former prisoner' becomes 'excon' (I've seen this before).
'hiding' indicates putting letters inside.
'record' becomes 'ep'.
'before' means one lot of letters go next to another.
'raised' says the letters should be written backwards.
'it' in reverse letter order is 'ti'.
'ep'+'ti'='epti'
'excon' placed around 'epti' is 'EXCEPTION'.
(Other definitions for exception that I've seen before include "The one that proves the rule" , "breach of rule" , "Something not following a rule" , "It's said to prove a rule" , "It doesn't conform to the general rule" .)