Crazy promotion in two thousand and one (6)
I believe the answer is:
madman
'crazy' is the definition.
(crazy can mean a mad person)
'promotion in two thousand and one' is the wordplay.
'promotion' becomes 'ad' (short for advert).
'in' indicates putting letters inside.
'two thousand' becomes 'mm'.
'and' says to put letters next to each other.
'one' becomes 'an' (an apple is one apple).
'ad' inserted into 'mm' is 'madm'.
'madm'+'an'='MADMAN'
(Other definitions for madman that I've seen before include "Reckless person" , "Lunatic" .)