Collect animal tails in the morning (5)
I believe the answer is:
amass
'collect' is the definition.
('amass' can be a synonym of 'collect')
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for amass that I've seen before include "Gather in great quantity" , "Sodium chloride" , "Be a compiler" , "Accrue, heap up" , "Put together" .)