One displays fashion line (5)
I believe the answer is:
'one' is the definition.
Both the definition and answer are adjectives. Perhaps they are linked in a way I don't understand?
'fashion line' is the wordplay.
'fashion' becomes 'mode' (synonyms).
'line' becomes 'l' (used when specifying particular lines from a poem).
'displays' acts as a link.
Can you help me to learn more?
(Other definitions for model that I've seen before include "Artist's sitter" , "She parades on the catwalk" , "Replica (on the catwalk?)" , "Moss, say" , "Miniature replica" .)