Attack dog's half-cut after two drops of beer (5)

I believe the answer is:

beset

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'attack' is the definition.
(besetting is a kind of attacking)

I can't explain the remainder of the clue.

(Other definitions for beset that I've seen before include "Encircled, attacked" , "Assail (with problems?)" , "Surround and harass" , "Beleaguer" , "plague" .)

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