In a US city see tailless pack animal (6)
I believe the answer is:
alpaca
'animal' is the definition.
(thesaurus)
'in a us city see tailless pack' is the wordplay.
'in' means one lot of letters goes inside another.
'us city' becomes 'la'.
'see tailless' means to remove the last letter.
'a'+'la'='ala'
'pack' with its final letter removed is 'pac'.
'ala' enclosing 'pac' is 'ALPACA'.
(Other definitions for alpaca that I've seen before include "Llama's relative" , "S American mammal related to the llama" , "Type of wool" , "Domesticated llama with long silky fleece" , "Llama relation" .)