Actors were first to have made a move on board (7)
I believe the answer is:
castled
'have made a move on board' is the definition.
I can't tell whether this defines the answer.
'actors were first' is the wordplay.
'actors' becomes 'cast' (group of actors).
'were first' becomes 'led'.
'cast'+'led'='CASTLED'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for castled that I've seen before include "Made a chess move" , "have moved on board" , "Performed chess move" , "defensive move" , "Moved king into safety" .)