Is confused with manilla envelope's content? (5,4)
I believe the answer is:
snail mail
'envelope's content?' is the definition.
I know nothing about this answer so I can't judge whether this works.
'is confused with manilla' is the wordplay.
'confused with' indicates anagramming the letters.
'is' anagrammed with 'manilla' gives 'SNAIL MAIL'.
Can you help me to learn more?
(Other definitions for snail mail that I've seen before include "Modern jargon for letter post, mollusc-slow compared to electronic transport" , "Postal system (facetious)" , "traditional post" , "old-fashioned correspondence?" , "Ordinary post" .)