Green politician's bottom appearing in new advert (7)
I believe the answer is:
verdant
'green' is the definition.
(I've seen this before)
'politician's bottom appearing in new advert' is the wordplay.
'bottom' suggests the final letters.
'appearing in' indicates putting letters inside.
'new' indicates anagramming the letters.
The last letter of 'politician' is 'n'.
'advert' anagrammed gives 'verdat'.
'n' inserted into 'verdat' is 'VERDANT'.
(Other definitions for verdant that I've seen before include "Having green growth" , "Unsophisticated" , "Leafy" , "Green like grass or fields" , "Covered with lush green grass or vegetation" .)