Clue: Vicar's upset collecting one pound in coins (6)
Answer: SILVER
Explanation: Definition: coins
 **Reversal of**(…'s upset, in a down clue) REV(form of address for a vicar)'S **containing**(collecting) [ I(Roman numeral for "one") + L(or £, symbol for pound sterling) ].
Defn: …, collectively, made of, or looking like they're made of, silver.