Creature emerging occasionally in spring (3)
I believe the answer is:
pig
'creature' is the definition.
(I've seen this in other clues)
'emerging occasionally in spring' is the wordplay.
'emerging occasionally in' means one should take alternating letters (letters taken at regular intervals).
The alternating letters of 'spring' are 'PIG'.
(Other definitions for pig that I've seen before include "Farm animal" , "Eat greedily" , "person who eats too much" , "Glutton" , "Unforged metal" .)