Animal's excessive sign of hesitation (5)
I believe the answer is:
otter
'animal's' is the definition.
(thesaurus)
'excessive sign of hesitation' is the wordplay.
'excessive' becomes 'ott' (short for 'over the top' - informal British).
'sign of hesitation' becomes 'er'.
'ott'+'er'='OTTER'
(Other definitions for otter that I've seen before include "carnivore is concerned" , "River animal" , "Aquatic weasel-like mammal" , "Freshwater brown carnivore" , "Something furry" .)