Flimsy paper kept in a folder (7)
I believe the answer is:
fragile
'flimsy' is the definition.
(thesaurus)
'paper kept in a folder' is the wordplay.
'paper' becomes 'rag' (rag is a kind of paper).
'kept in' means one lot of letters goes inside another.
'a folder' becomes 'file' (file folder is a kind of folder).
'rag' placed inside 'file' is 'FRAGILE'.
(Other definitions for fragile that I've seen before include "Delicate; easily broken" , "Delicate, tenuous" , "Rag file is easily broken" , "Easily-damaged" , "Brittle" .)