Crumpled horn protecting one animal (5)
I believe the answer is:
rhino
'animal' is the definition.
(short for rhinoceros)
'crumpled horn protecting one' is the wordplay.
'crumpled' indicates an anagram (a crumbled or damaged version of the letters).
'protecting' means one lot of letters goes inside another (inserted letters are held or protected).
'one' becomes 'i' (Roman numeral).
'horn' anagrammed gives 'rhno'.
'rhno' placed around 'i' is 'RHINO'.
(Other definitions for rhino that I've seen before include "old money?" , "I may make fearsome charges" , "Large horned mammal" , "Horned ungulate" , "old-fashioned bread" .)