Ordering pears, I have ambition (6)
I believe the answer is:
aspire
'have ambition' is the definition.
(I've seen this before)
'ordering pears i' is the wordplay.
'ordering' indicates anagramming the letters.
'pears'+'i'='pearsi'
'pearsi' anagrammed gives 'ASPIRE'.
(Other definitions for aspire that I've seen before include "Is a rep (anag.)" , "Desire (to reach higher things)" , "Aim, have an ambitious plan" , "Seek (to do something)" , "Aim (for higher things)" .)