You bet after lone card originally turned? Fold! (9)
I believe the answer is:
enclosure
'fold' is the definition.
(thesaurus)
'you bet after lone card originally turned?' is the wordplay.
'you bet' becomes 'sure' (I've seen this in another clue).
'after' says to put letters next to each other.
'originally' indicates taking the first letters.
'turned?' is an anagram indicator.
The initial letter of 'card' is 'c'.
'lone'+'c'='lonec'
'lonec' is an anagram of 'enclo'.
'sure' put after 'enclo' is 'ENCLOSURE'.
(Other definitions for enclosure that I've seen before include "Pen" , "pound" , "One's contained" , "Sealed-off area" , "What's in the envelope" .)