Venomous reptile, one intelligent, hoping for success (12)
I believe the answer is:
aspirational
'hoping for success' is the definition.
(aspiring to success)
'venomous reptile one intelligent' is the wordplay.
'venomous reptile' becomes 'asp' (venomous snake).
'one' becomes 'I' (Roman numeral).
'intelligent' becomes 'rational' (similar in meaning).
'asp'+'i'+'rational'='ASPIRATIONAL'
(Other definitions for aspirational that I've seen before include "Like those trying to succeed" , "Characterised by hope or ambition" , "Characterised by a desire to be successful" , "Pertaining to hopes" , "After a role model" .)