Copying narrow brooch in silver case (5)
I believe the answer is:
aping
'copying' is the definition.
('ape' can be a synonym of 'copy')
'narrow brooch in silver case' is the wordplay.
I cannot quite understand how this works, but
'brooch' could be 'pin' (decorative item pinned to clothing) and 'pin' is present in the answer.
'silver' could be 'ag' (Ag is the chemical symbol for silver) and 'ag' is found within the leftover letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for aping that I've seen before include "Imitating, copying" , "Acting like a parrot" , "Parroting" , "Mimicking like monkey" , "Trying to repeat" .)