Synthetic cobbler’s model featured in illustration (7)
I believe the answer is:
plastic
'synthetic' is the definition.
(plastic is a synthetic material)
'cobbler's model featured in illustration' is the wordplay.
'cobbler's model' becomes 'last' (device used by a cobbler).
'featured in' indicates putting letters inside.
'illustration' becomes 'pic' (short for picture).
'last' inserted inside 'pic' is 'PLASTIC'.
(Other definitions for plastic that I've seen before include "Euphemism for a credit card" , "Easily shaped/moulded" , "means of deferring payment" , "Flexible - synthetic material" , "Artificial/synthetic" .)