Terminate king and I will follow (4)
I believe the answer is:
kill
'terminate' is the definition.
(I know that kill is a kind of terminate)
'king and i will follow' is the wordplay.
'king' becomes 'k' (chess abbreviation).
'and' means one lot of letters go next to another.
'will' becomes 'll' (contracted form, as in 'he'll' - 'he will').
'follow' is a charade indicator (letters next to each other).
'k'+'i'+'ll'='KILL'
(Other definitions for kill that I've seen before include "Prey" , "Murder" , "Destroy" , "bag?" , "Slay" .)