Toreador whirls, primarily to confuse bull (7)
I believe the answer is:
twaddle
'bull' is the definition.
(thesaurus)
'toreador whirls primarily to confuse' is the wordplay.
'primarily' says to take the initial letters.
'to confuse' becomes 'addle' (addling is a kind of confusing).
The first letters of 'toreador whirls' is 'tw'.
'tw'+'addle'='TWADDLE'
(Other definitions for twaddle that I've seen before include "Trivial speech or writing" , "Balderdash" , "bunk" , "Bull" , "tripe" .)