Animal or snake with a peculiar tail (4)
I believe the answer is:
boar
'animal' is the definition.
(I've seen this before)
'snake with a peculiar tail' is the wordplay.
'snake' becomes 'boa' (boa is a kind of snake).
'with' means one lot of letters go next to another.
'tail' says to take the final letters.
The final letter of 'peculiar' is 'r'.
'boa'+'r'='BOAR'
'or' is the link.
(Other definitions for boar that I've seen before include "The head for drink Falstaff had" , "Uncastrated male pig" , "Resting place for birds or bats" , "Uncastrated male hog" , "Wild swine" .)