Extend professional area (8)
I believe the answer is:
protract
'extend' is the definition.
('protract' can be a synonym of 'extend')
'professional area' is the wordplay.
'professional' becomes 'pro' ('pro' can be a synonym of 'professional').
'area' becomes 'tract' (tract is a kind of area**).
'pro'+'tract'='PROTRACT'
(Other definitions for protract that I've seen before include "Increase" , "Drag out at length" , "Extend length" , "Draw out, lengthen the time" , "Stretch out" .)