Old man can start to appreciate film (6)
I believe the answer is:
patina
'film' is the definition.
(I've seen this before)
'old man can start to appreciate' is the wordplay.
'old man' becomes 'pa' (both can mean father).
'can' becomes 'tin' (synonyms).
'start to' says to take the initial letters.
The first letter of 'appreciate' is 'a'.
'pa'+'tin'+'a'='PATINA'
(Other definitions for patina that I've seen before include "Film forming on bronze" , "Surface film formed by age" , "Sheen produced by age and polishing" , "Surface coating that comes with age" , "Fine layer on the surface, laid down over time" .)