Prolific detective might become dull they say (7)

I believe the answer is:

maigret

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

'prolific detective' is the definition.
'maigret' can be an answer for 'detective' (I've seen this before). I am not certain of the 'prolific' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for maigret that I've seen before include "Fictional detective" , "cracker?" , "Policeman" , "Simenon's Inspector" , "Simenon''s detective-superintendent" .)

I've seen this clue in The Irish Times.

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