Investment of capital possibly (5)

I believe the answer is:

siege

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'investment' is the definition.
(investment can mean a siege)

I cannot understand how the rest of the clue works.

(Other definitions for siege that I've seen before include "Military operation ringing a town" , "Operation to surround and cut off supplies" , "Persistent attack" , "Operation to surround a town/fortress" , "Military operation cutting off access" .)

I've seen this clue in The Globe and Mail.

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