We hear officers are at the heart of things (7)

I believe the answer is:

kernels

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'we hear officers' is the definition.
I can't tell whether this defines the answer.

'at the heart of things' is the wordplay.
'at' means one lot of letters go next to another.
'the heart' becomes 'kernel' (synonyms).
'of things' becomes 's' (I can't explain this - if you can you should give a lot more credence to this answer).
'kernel'+'s' is 'KERNELS'.

'are' is the link.

Can you help me to learn more?

(Another definition for kernels that I've seen is " Centre parts of nuts".)

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

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