Head of state bumped off expert (7)
I believe the answer is:
skilled
'expert' is the definition.
(similar in meaning)
'head of state bumped off' is the wordplay.
'head of' says to take the initial letters.
'bumped off' becomes 'killed' (I've seen this in another clue).
The first letter of 'state' is 's'.
's'+'killed'='SKILLED'
(Other definitions for skilled that I've seen before include "Showing expertise" , "Talented" , "Adept, clever" , "Expert, adroit" , "Proficient" .)