Club without openers for opening day (4)
I believe the answer is:
wood
'club' is the definition.
(wood is a kind of club)
'without openers for opening day' is the wordplay.
'without' becomes 'wo' (abbreviation of 'without', normally with a slash).
'openers for' suggests taking the first letters.
The first letters of 'opening day' is 'od'.
'wo'+'od'='WOOD'
(Other definitions for wood that I've seen before include "Concert promoter" , "'Under Milk - - ' (lit.)" , "Kind of musical instrument" , "celebrated conductor" , "Lots of trees" .)