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' means one lot of letters goes inside another.
'two thousand' becomes 'mm'.
'and' is a charade indicator (letters next to each other).
'one' becomes 'an' (an apple is one apple).
'ad' inserted inside 'mm' is 'madm'.
'madm'+'an'='MADMAN'
(Other definitions for madman that I've seen before include "Reckless person" , "Lunatic" .)