Collect a donkey in the morning (5)
I believe the answer is:
amass
'collect' is the definition.
(I know that collect is a more specific form of the action amass)
'a donkey in the morning' is the wordplay.
'donkey in the morning' becomes 'mass' (I can't justify this - if you can you should believe this answer much more).
'a'+'mass'='AMASS'
Can you help me to learn more?
(Other definitions for amass that I've seen before include "Stockpile" , "Build up" , "Gather in great quantity" , "Accumulate over time" , "Be a compiler" .)