Stop tailless pet's sign of affection outside comprehensive (8)
I believe the answer is:
catholic
'comprehensive' is the definition.
(thesaurus)
'stop tailless pet's sign of affection outside' is the wordplay.
I cannot really understand how this works, but
'of' could be 'o' and 'o' is found in the answer.
'pet' could be 'cat' (cats are often kept as pets) and 'cat' is found within the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for catholic that I've seen before include "All embracing" , "(Of tastes) wide-ranging" , "Broad" , "Eclectic" , "Showing widespread sympathy" .)