Lovers yell their heads off and exaggerate their merits (8)

I believe the answer is:

oversell

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'lovers yell' is the definition.
The definition suggests a verb in its base form which matches the answer.

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

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(Another definition for oversell that I've seen is " Exaggerate merits".)

I've seen this clue in the Sydney Morning Herald.

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