Stuff plenty into the outer parts of a couch (5)
I believe the answer is:
cloth
'stuff' is the definition.
(thesaurus)
'plenty into the outer parts of a couch' is the wordplay.
'plenty' becomes 'lot' (I can't explain this - if you can you should believe this answer much more).
'into' means one lot of letters goes inside another.
'the outer parts of' says to hollow out the word (remove centre letters).
'couch' with its middle taken out is 'ch'.
'lot' going inside 'ch' is 'CLOTH'.
Can you help me to learn more?
(Other definitions for cloth that I've seen before include "Fabric, textile" , "Woven material" , "Gingham, say" , "ministers" , "Textiles" .)