Furniture item seen in lots of advertisements (4)
I believe the answer is:
sofa
'furniture item' is the definition.
'in lots of advertisements' is the wordplay.
'in' says the answer is hidden in the clue.
'SOFA' can be found hidden inside 'lots of advertisements'.
'seen' acts as a link.
(Other definitions for sofa that I've seen before include "Couch" , "Living room seat" , "Item of furniture" , "Upholstered seating" , "Upholstered seat for two or more" .)