Blunt criticism of decent chap joining club (8)
I believe the answer is:
Here is my best explanation:
'blunt criticism' is the definition.
(I've seen this before)
'decent chap joining club' is the wordplay.
'decent chap' becomes 'brick' (I've seen this in other clues).
'joining' says to put letters next to each other.
'club' becomes 'bat' (bat is a kind of club).
'of' acts as a link.
(Other definitions for brickbat that I've seen before include "Missile, criticism", "Hostile criticism - missile", "An uncomplimentary remark, or kind of missile", "Highly critical remark", "(Critic's) weapon", "Criticism", "Blunt criticism", "Strong criticism", "Building block used as missile" and "Critical remark".)