Learning to ignore last boss (4)
I believe the answer is:
stud
'boss' is the definition.
(both can mean a metal decoration)
'learning to ignore last' is the wordplay.
'learning' becomes 'study' (study is a kind of learning).
'to ignore last' means to remove the last letter (I've seen 'ignoring last' mean this).
'study' with its last letter taken away is 'STUD'.
(Other definitions for stud that I've seen before include "gambling with cards" , "Macho - stables - boss" , "Stallion kept for breeding" , "Animal kept for breeding" , "Press fastener" .)