Nanny's forged surname and identity (9)
I believe the answer is:
nursemaid
'nanny's' is the definition.
('nursemaid' can be a synonym of 'nanny')
'forged surname and identity' is the wordplay.
'forged' indicates anagramming the letters.
'and' means one lot of letters go next to another.
'identity' becomes 'id' (I've seen this in other clues).
'surname' is an anagram of 'nursema'.
'nursema'+'id'='NURSEMAID'
(Other definitions for nursemaid that I've seen before include "tender" , "Childminder" , "Alice, for example" , "Girl tending young children" , "One looking after children" .)