The guy's introduced first name into the layers (4)
I believe the answer is:
hens
'the layers' is the definition.
The answer and definition can be both animals as well as being plural nouns.
Maybe they are linked in a way I don't understand?
'the guy's introduced first name' is the wordplay.
'the guy' becomes 'he'.
'introduced' becomes 's' (I am not sure about this - if you are sure you should believe this answer much more).
'first' is a charade indicator (letters next to each other).
'name' becomes 'n' (common abbreviation e.g. on forms).
's' after 'n' is 'ns'.
'he'+'ns'='HENS'
'into' acts as a link.
Can you help me to learn more?
(Other definitions for hens that I've seen before include "Female chickens" , "Birds kept for laying" , "Female birds" , "Adult chickens" , "Poultry" .)