Possible pollutant finally wrapped in film (7)
I believe the answer is:
plastic
'possible pollutant' is the definition.
The definition and answer can be both substances as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'finally wrapped in film' is the wordplay.
'finally' becomes 'last' (synonyms).
'wrapped in' is an insertion indicator.
'film' becomes 'pic' (short for picture).
'last' going inside 'pic' is 'PLASTIC'.
Can you help me to learn more?
(Other definitions for plastic that I've seen before include "Scalp it badly to make a synthetic material" , "Lips act as a synthetic material" , "Unattractively synthetic" , "Like some cards" , "Synthetic polymer" .)