Animals:
* Foxtail
* Horsetail
* Rattlesnake tail
* Wombat tail
Other:
* Bobtail (short-tailed, as in a bobtail dog)
* Pigtail (a braid of hair)
* Sailboat tail
* Whippet tail (a type of racing dog)
* Longtail (as in a longtail boat)
Figurative:
* Wagging tail (a happy, excited feeling)
* Tale-tail (a term sometimes used to indicate the end of a story)
Let me know if you'd like more examples or if you're looking for compound words with a specific meaning!