The beast gives a growl when measures are interrupted (6)
I believe the answer is:
ferret
But I can't explain it at all! Could you help me understand?
(Other definitions for ferret that I've seen before include "Small member of weasel family, good for catching rabbits" , "Search about persistently" , "Root around" , "Type of polecat -- or silk binding tape" , "Small weasel good at hunting rabbits" .)