Some had seen commercials (3)
I believe the answer is:
ads
'commercials' is the definition.
(advertisements)
'some had seen' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'ADS' can be found hidden inside 'had seen'.
(Other definitions for ads that I've seen before include "Classifieds (abbr)" , "Notices" , "Commercials" , "Promotions" .)