In the end handler retires these unruly dogs (8)
I believe the answer is:
terriers
'dogs' is the definition.
(terrier is a kind of dog)
'in the end handler retires these unruly' is the wordplay.
'in the end' suggests the final letters.
'these unruly' indicates anagramming the letters.
The final letter of 'handler' is 'r'.
'r'+'retires'='rretires'
'rretires' with letters rearranged gives 'TERRIERS'.
(Other definitions for terriers that I've seen before include "eg Skye, Cairn and 18" , "Airedales, for example" , "Part-time soldiers" , "Small short-bodied breeds of dogs" .)