Crossword Genius

Expert on board relative's trailer when train missed (11)

Ross

I believe the answer is:

grandmaster

'expert on board' is the definition.
(expert at chess - a board game)

I can't explain the rest of the clue.

(Other definitions for grandmaster that I've seen before include "Star chess player" , "a wizard with his pieces?" , "A top chess player" , "Expert on board" , "Chess player of the highest class" .)

I've seen this clue in The Independent.
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