### Clue: Hold tailless mammal back pretty quickly (10)
### Answer: ALLEGRETTO 
 ### Explanation: Definition: pretty quickly
 "allege"(to hold/to claim or assert something without proof) **minus its last letter**(tailless) + **reversal of**(… back) OTTER(a semi-aquatic mammal).
Defn: A musical direction to play pretty/fairly quickly, but not as fast as with allegro.