Fed old lady good new sandwiches (1-3)
I believe the answer is:
g-man
'fed' is the definition.
(I've seen this before)
'old lady good new sandwiches' is the wordplay.
'old lady' becomes 'ma' (both can mean mother).
'good' becomes 'g' (abbreviation).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'sandwiches' is an insertion indicator (goes on either side like a sandwich).
'g'+'n'='gn'
'ma' going within 'gn' is 'G-MAN'.
(Other definitions for g-man that I've seen before include "FBI agent" , "Officer of the FBI in USA" .)