JFK (7)
I believe the answer is:
kennedy
'jfk' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for kennedy that I've seen before include "Nigel -, Br. violinist" , "US president, d. 1963" , "Murdered US president" , "US president assassinated in Dallas" , "Youngest US President" .)