Butterflies eat rump steak to start with (12)
I believe the answer is:
swallowtails
'butterflies' is the definition.
(I've seen this before)
'eat rump steak to start with' is the wordplay.
I cannot really understand how this works, but
'eat' could be 'swallow' (I've seen this before) and 'swallow' is present in the answer.
'rump' could be 'tail' (synonyms) and 'tail' is present in the answer.
A single letter 's' remains which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for swallowtails that I've seen is " butterflies".)