Notice one model, concerned with fat (7)
I believe the answer is:
'concerned with fat' is the definition.
(as in adipose tissue)
'notice one model' is the wordplay.
'notice' becomes 'ad' (short for advert).
'one' becomes 'i' (Roman numeral).
'model' becomes 'pose' (model can mean to pose).
(Other definitions for adipose that I've seen before include "Of tissue, fatty in substance" , "Of animal, fat, fatty" , "Relating to fat" , "Like fatty tissue" , "Composed of animal fat" .)