It may consist of cards in packs, as stated (5)
I believe the answer is:
index
'it may consist of cards' is the definition.
(index cards)
'in packs as stated' is the wordplay.
I cannot quite see how this works, but
'in' is found in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for index that I've seen before include "list of unreadable books" , "A-Z listing" , "Alphabetical guide" , "Alphabetical listing and first finger" , "Alphabetical list of items" .)