Letter opener that is removed from armoire, admired as quirky (4,3,2,5)
I believe the answer is:
dear sir or madam
'letter opener' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'that is removed from armoire admired as quirky' is the wordplay.
'that is' becomes 'ie' (abbreviation for id est, 'that is' in Latin).
'removed from' indicates named letters should be taken away.
'quirky' is an anagram indicator.
'armoire'+'admired'+'as'='armoireadmiredas'
'armoireadmiredas' with 'ie' taken out is 'armoradmiredas'.
'armoradmiredas' with letters rearranged gives 'DEAR SIR OR MADAM'.
Can you help me to learn more?
(Another definition for dear sir or madam that I've seen is " Formal introduction".)