One advantage of new seats (5)
I believe the answer is:
asset
'one advantage' is the definition.
(I've seen this before)
'new seats' is the wordplay.
'new' is an anagram indicator.
'seats' with letters rearranged gives 'ASSET'.
'of' is the link.
(Other definitions for asset that I've seen before include "Valuable possession, worth having" , "Item conferring advantage" , "Help" , "Boon" , "A useful thing l" .)