Plain wrapping totally loose (6)
I believe the answer is:
fallen
'loose' is the definition.
The answer and definition are different parts of speech. However, adjectives and past participle verbs can occasionally mean the same thing.
'plain wrapping totally' is the wordplay.
'plain' becomes 'fen' (I can't explain this - if you can you should give a lot more credence to this answer).
'wrapping' means one lot of letters goes inside another.
'totally' becomes 'all'.
'fen' going around 'all' is 'FALLEN'.
Can you help me to learn more?
(Other definitions for fallen that I've seen before include "disgraced" , "Killed in battle" , "Seduced" , "How Babylon is" , "Having sinned or surrendered" .)