What protects the ankle from fierce animal, it's said (6)
I believe the answer is:
gaiter
'what protects the ankle' is the definition.
(protective clothing worn on legs)
'fierce animal it's said' is the wordplay.
'fierce animal' becomes 'gator' (short for alligator).
'it's said' shows a homophone (sound like).
'gator' is a homophone of 'GAITER'.
'from' is the link.
(Other definitions for gaiter that I've seen before include "Legging to cover ankle and instep" , "Ankle and lower leg cover" , "Legging or spat" , "Lower leg covering" , "Leg cover, spat" .)