Primate's boob (6)

I believe the answer is:

howler

I believe this is a double definition.

'primate's' is the first definition.
(howler is a kind of primate)

'boob' is the second definition.
(both can mean an embarrassing mistake)

(Other definitions for howler that I've seen before include "Serious avoidable mistake" , "A glaring mistake, perhaps by schoolboy" , "Glaring mistake made by schoolboy" , "Serious blunder" , "A monkey; a bad mistake" .)

I've seen this clue in The Guardian.

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