Biting into current identity (4)
I believe the answer is:
acid
'biting' is the definition.
(I've seen this before)
'current identity' is the wordplay.
'current' becomes 'ac' (alternating current).
'identity' becomes 'id' (I've seen this in other clues).
'ac'+'id'='ACID'
'into' acts as a link.
(Other definitions for acid that I've seen before include "bad rain" , "Acerbic" , "Corrosive substance" , "Sharp - tart - kind of house party" , "Polluted precipitation" .)