Mount off-shore (5)
I believe the answer is:
horse
'mount' is the definition.
(I know that mount can be written as horse)
'off-shore' is the wordplay.
'off' indicates an anagram.
'shore' is an anagram of 'HORSE'.
(Other definitions for horse that I've seen before include "Domesticated animal" , "Equipment in gym" , "runner" , "Its mouth a reliable source of info" , "Eg, mare" .)