Fantastic price made one want to do it now (5,4)
I believe the answer is:
carpe diem
'one want to do it now' is the definition.
(Latin phrase meaning 'seize the day')
'fantastic price made' is the wordplay.
'fantastic' indicates anagramming the letters.
'price'+'made'='pricemade'
'pricemade' anagrammed gives 'CARPE DIEM'.
(Other definitions for carpe diem that I've seen before include "from Horace" , "Make the most of the present" , "Seize occasion" , "'Seize the day'" , "Make the most of the time you have" .)