Store of money for 100 volunteers (7)

I believe the answer is:

coffers

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'store of money for 100 volunteers' is the definition.
I can't tell whether this definition defines the answer.

'100 volunteers' is the wordplay.
'100' becomes 'C' (Roman numeral).
'volunteers' becomes 'offers' ('offer' can be a synonym of 'volunteer').
'c'+'offers'='COFFERS'

Can you help me to learn more?

(Other definitions for coffers that I've seen before include "Treasury funds" , "Supply of funds" , "Treasury box" , "containers" , "Financial resources or money boxes" .)

I've seen this clue in The Daily Express.

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