Words to explain part of race coming to conclusion (6)
I believe the answer is:
legend
'words to explain' is the definition.
(legend can mean a key eg on a map)
'part of race coming to conclusion' is the wordplay.
'part of race' becomes 'leg' (eg a leg of a relay).
'coming to' is a charade indicator (letters next to each other).
'conclusion' becomes 'end' (something's conclusion is its end).
'leg'+'end'='LEGEND'
(Other definitions for legend that I've seen before include "Story that may be untrue" , "Key" , "Superstar" , "explanation" , "Caption; very well known" .)