Prince investing millions in carriage (4)

I believe the answer is:

amir

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'prince' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps they are linked in a way I don't understand?

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for amir that I've seen before include "Old ruler" , "Moslem leader's here" , "See ruler" , "Muslim ruler" .)

I've seen this clue in The Sunday Times and The Times.

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