Shortened advert about a game (8)
I believe the answer is:
abridged
'shortened' is the definition.
('abridge' can be a synonym of 'shorten')
'advert about a game' is the wordplay.
'advert' becomes 'ad' (synonyms).
'about' indicates putting letters inside.
'a game' becomes 'bridge' (card game).
'ad' going around 'bridge' is 'ABRIDGED'.
(Other definitions for abridged that I've seen before include "Shortened as book may be" , "Cut short - big adder (anag)" , "Shorter" , "Epitomised" , "Abbreviated, contracted" .)