Fat individual taken in by modern-day attitude (7)
I believe the answer is:
adipose
'fat' is the definition.
('adipose' can be similar in meaning to 'fat')
'individual taken in by modern-day attitude' is the wordplay.
'individual' becomes 'i'.
'taken in by' is an insertion indicator.
'modern day' becomes 'ad' (I've seen this in other clues).
'attitude' becomes 'pose' (I've seen this before).
'ad'+'pose'='adpose'
'i' inserted inside 'adpose' is 'ADIPOSE'.
(Other definitions for adipose that I've seen before include "Fat-storing (tissue)" , "Like fatty tissue" , "Of tissue, fatty in substance" , "Containing fat" , "Like a sort of fat" .)