Maybe club directors' material (9)
I believe the answer is:
cardboard
'material' is the definition.
(I know that cardboard is a material)
'maybe club directors'' is the wordplay.
'maybe club' becomes 'card' (clubs is a playing card suit).
'directors'' becomes 'board' (board of directors).
'card'+'board'='CARDBOARD'
(Other definitions for cardboard that I've seen before include "without substance" , "stiff material" , "A stiff thick paper" .)