Former partner, impudent, sees specialist (6)
I believe the answer is:
expert
'specialist' is the definition.
(a specialist is an expert in a field)
'former partner impudent' is the wordplay.
'former partner' becomes 'ex' (an ex-partner).
'impudent' becomes 'pert' (I've seen this before).
'ex'+'pert'='EXPERT'
'sees' is the link.
(Other definitions for expert that I've seen before include "Knowledgeable specialist" , "Dab hand" , "Highly skilled or knowledgeable person" , "One has specialist knowledge or ability" , "Buff" .)