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 subsidiary indication.
'decent chap' becomes 'brick' (I've seen this in other clues).
'joining' is a charade indicator (letters next to each other).
'club' becomes 'bat' (bat is a kind of club).
'of' is the link.
(Other definitions for brickbat that I've seen before include "(Critic's) weapon", "Missile, criticism", "Hostile criticism - missile", "Highly critical remark", "Critical remark", "An uncomplimentary remark, or kind of missile", "Blunt criticism", "Building block used as missile" and "Piece of blunt criticism".)