2 where she requires a card to play (8)
I believe the answer is:
charades
'2' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'she requires a card to play' is the wordplay.
'requires' is a charade indicator (letters next to each other).
'to play' indicates anagramming the letters.
'she'+'a'+'card'='sheacard'
'sheacard' anagrammed gives 'CHARADES'.
'where' is the link.
Can you help me to learn more?
(Other definitions for charades that I've seen before include "Guessing game where words are acted out" , "Party guessing game" , "Miming games" , "Miming parlour game" , "Game in which answers are acted out" .)