Commercial has to avoid including director’s head (6)
I believe the answer is:
advert
'commercial' is the definition.
(I've seen this before)
'to avoid including director's head' is the wordplay.
'to avoid' becomes 'avert' ('avert' can be a synonym of 'avoid'**).
'including' means one lot of letters goes inside another.
'head' says to take the initial letters.
The initial letter of 'directors' is 'd'.
'avert' enclosing 'd' is 'ADVERT'.
'has' acts as a link.
(Other definitions for advert that I've seen before include "Commercial notice" , "Draw attention to" , "Promotional display" , "Trailer" , "Promotional notice" .)