Light anchor king found on border (5)
I believe the answer is:
kedge
'light anchor' is the definition.
(I've seen this in another clue)
'king found on border' is the wordplay.
'king' becomes 'K' (abbreviation for king in chess).
'found on' means one lot of letters go next to another.
'border' becomes 'edge' (synonyms).
'k'+'edge'='KEDGE'
(Other definitions for kedge that I've seen before include "Light anchor" , "Small anchor" , "Move boat" , "Use hawser" , "Lively" .)