Academic specialisation for an agronomist? (5,2,5)

I believe the answer is:

field of study

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This could be a double definition.

'academic specialisation' is the first definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'an agronomist?' is the second definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.

'for' acts as a link.

Can you help me to learn more?

I've seen this clue in the Sydney Morning Herald.

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