A bad time to tickle guitarist in stomach? (7)

I believe the answer is:

midriff

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

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

(Other definitions for midriff that I've seen before include "Part of body between waist and chest" , "Region between chest and waist" , "Waistline area" , "Tummy area" , "Area between stomach and chest" .)

I've seen this clue in The Independent.

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