Fischer's forte (5)
I believe the answer is:
chess
'fischer's forte' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for chess that I've seen before include "board meeting" , "that has over thirty men on board" , "activity aimed at downfall of a king" , "Board game of 13, 16 and 21" , "Game involving mates" .)