Expert politician, Kennedy could be motivated (8)
I believe the answer is:
prompted
'motivated' is the definition.
('prompt' can be a synonym of 'motivate')
'expert politician kennedy' is the wordplay.
'expert' becomes 'pro' (short for professional).
'politician' becomes 'MP' (Member of Parliament).
'kennedy' becomes 'ted' (US senator Ted Kennedy, 1932-2009).
'pro'+'mp'+'ted'='PROMPTED'
'could be' acts as a link.
(Other definitions for prompted that I've seen before include "Given help with speech" , "Instigated" .)