Ostler regularly follows shy creature (6)
I believe the answer is:
coyote
'creature' is the definition.
(type of animal)
'ostler regularly follows shy' is the wordplay.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
'follows' says to put letters next to each other.
'shy' becomes 'coy' (coy can mean shy or modest).
The alternate letters of 'ostler' are 'ote'.
'ote' after 'coy' is 'COYOTE'.
(Other definitions for coyote that I've seen before include "North American prairie wolf" , "howler" , "US wild dog" , "-- State, South Dakota" , "North American animal" .)