The chap at the students' fete appearing as a scrap merchant (6)

'a scrap merchant' is the definition.
The definition suggests a singular noun which matches the answer.

'the chap at the students' fete appearing' is the wordplay.
'the chap' becomes 'man' (chap can mean a man).
'at' is a charade indicator (letters next to each other) (I've seen this in other clues).
'the students' fete appearing' becomes 'rag' (I can't explain this - if you can you should believe this answer much more).
'man' after 'rag' is 'RAGMAN'.

'as' acts as a link.

Can you help me to learn more?