Bigwigs initially need directors to supply teaching aid
I believe the answer is:
blackboard
'teaching aid' is the definition.
(I've seen this before)
'bigwigs initially need directors' is the wordplay.
'initially' indicates taking the first letters.
'need' becomes 'lack' (lack is a kind of need**).
'directors' becomes 'board' (I've seen this before).
The first letter of 'bigwigs' is 'b'.
'b'+'lack'+'board'='BLACKBOARD'
'to supply' acts as a link.
(Other definitions for blackboard that I've seen before include "something to write on" , "Teaching aid" , "Surface for chalk" , "school equipment" , "where he might chalk up a win" .)