I sold cigar to desperate doctor who shouldn't encourage smoking (12)

I believe the answer is:

cardiologist

I'm a little stuck... Click here to teach me more about this clue!

'doctor who shouldn't encourage smoking' is the definition.
'cardiologist' can be an answer for 'doctor' (cardiologist is a kind of doctor). I am unsure of the rest of the definition.

'i sold cigar to desperate' is the wordplay.
'desperate' indicates anagramming the letters (a desperate or pathetic spelling).
'i'+'sold'+'cigar'+'to'='isoldcigarto'
'isoldcigarto' anagrammed gives 'CARDIOLOGIST'.

Can you help me to learn more?

(Another definition for cardiologist that I've seen is " Specialist in heart disease".)

I've seen this clue in The Irish Times.

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