Feature that could be made of tin and enamel (9)
I believe the answer is:
lineament
'feature' is the definition.
('lineament' can be a synonym of 'feature')
'made of tin and enamel' is the wordplay.
'made of' indicates an anagram.
'and' means one lot of letters go next to another (I've seen this in other clues).
'tin' put after 'enamel' is 'enameltin'.
'enameltin' is an anagram of 'LINEAMENT'.
'that could be' is the link.
(Other definitions for lineament that I've seen before include "distinguishing feature" , "Distinctive character" , "(Facial) feature" .)