The origins of interesting old tale about Whit (4)
I believe the answer is:
iota
'whit' is the definition.
('iota' can be a synonym of 'whit')
'the origins of interesting old tale about' is the wordplay.
'the origins of' says to take the initial letters.
The initial letters of 'interesting old tale about' is 'IOTA'.
(Other definitions for iota that I've seen before include "Contrivance" , "Jot or tittle" , "Trace" , "Tiny bit" , "very small part" .)