Bound leaves up, with page slotted in (8)
I believe the answer is:
Here is my best explanation:
'bound' is the definition.
(strapping is a kind of binding)
'up with page slotted in' is the wordplay.
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'with' indicates putting letters inside.
'page' becomes 'p'.
'slotted in' becomes 'departs' (I can't explain this - if you can you should believe this answer much more).
'p' going into 'departs' is 'depparts'.
'depparts' written backwards gives 'STRAPPED'.
'leaves' is the link.
(Other definitions for strapped that I've seen before include "in need of money", "beaten", "Bound", "Secured; short of money", "Short of money", "broke", "punished", "whipped", "- - for cash (hard up)" and "affected by shortage".)