Knowing about old pages becoming loose (6)
I believe the answer is:
floppy
'loose' is the definition.
(thesaurus)
'knowing about old pages' is the wordplay.
'knowing' becomes 'fly' (**).
'about' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'pages' becomes 'pp'.
'o'+'pp'='opp'
'fly' placed around 'opp' is 'FLOPPY'.
'becoming' is the link.
(Other definitions for floppy that I've seen before include "Limp, flexible" , "Bendy" , "Limp - computer disk" , "Opposed to firm" , "Sort of disk" .)