Prepares to capture rook, say, in carefully planned moves (3,6)
I believe the answer is:
set pieces
'carefully planned moves' is the definition.
Although both the answer and definition are plural nouns, I can't see how one could define the other.
'prepares to capture rook say' is the wordplay.
'prepares' becomes 'sets' ('set' can be a synonym of 'prepare').
'to capture' is an insertion indicator.
'rook say' becomes 'piece' (rook is a kind of piece).
'sets' going around 'piece' is 'SET PIECES'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for set pieces that I've seen before include "bishops and others?" , "rehearsed moves" , "Well-practised moves" , "Elaborate formal speeches" , "men on chess board?" .)