Desire to get on? No, I'm a bit sloppy! (8)
I believe the answer is:
ambition
'desire to get on?' is the definition.
(I've seen this before)
'no i'm a bit sloppy' is the wordplay.
'sloppy' indicates anagramming the letters.
'no'+'im'+'a'+'bit'='noimabit'
'noimabit' anagrammed gives 'AMBITION'.
(Other definitions for ambition that I've seen before include "Desire to succeed in the world" , "Strong desire for success" , "hope for the future" , "Desire to get on" , "Objective" .)