Fool showing origin of Tarot card (4)
I believe the answer is:
twit
'fool' is the definition.
(thesaurus)
'origin of tarot card' is the wordplay.
'origin of' indicates taking the first letters.
'card' becomes 'wit' ('wit' can be a synonym of 'card').
The initial letter of 'tarot' is 't'.
't'+'wit'='TWIT'
'showing' is the link.
(Other definitions for twit that I've seen before include "Idiot; tease" , "Bait - fool" , "Ninny" , "Twerp" , "Stupid person" .)