Roman reformer firm at heart (4)

I believe the answer is:

cato

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'roman' is the definition.
(I've seen this before)

'firm at heart' is the wordplay.
'firm' becomes 'co' (abbreviation for company).
'heart' means one lot of letters goes inside another.
'co' enclosing 'at' is 'CATO'.

'reformer' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for cato that I've seen before include "classical writer" , "Ancient Roman censor" , "Marcus Porcius - , Roman politician, censor" , "Senator" , "Roman statesman" .)

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

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