After a heady victory, the little beasts lose badly (5)
I believe the answer is:
voles
'after a heady victory the little beasts' is the definition.
I can't tell whether this defines the answer.
'lose badly' is the wordplay.
I cannot really understand how this works, but
an anagram of 'lose' is 'oles' which is present in the answer.
A single letter 'v' remains which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Another definition for voles that I've seen is " Mouse-like rodents found in fields and meadows".)