Model and I do business (5)
I believe the answer is:
ideal
'model' is the definition.
(ideal can mean model or perfect)
'i do business' is the wordplay.
'do business' becomes 'deal' (as in dealing with another business).
'i'+'deal'='IDEAL'
'and' is the link.
(Other definitions for ideal that I've seen before include "Perfect; visionary" , "Just perfect, couldn't be better" , "Optimal" , "Paradigm" , "faultless" .)