Butterfly perched on the first down, regularly (5)
I believe the answer is:
satyr
'butterfly' is the definition.
(I've seen this before)
'perched on the first down regularly' is the wordplay.
I cannot quite understand how this works, but
'perched' could be 'sat' (I've seen this before) and 'sat' is present in the answer.
This may be the basis of clue (or it may be nonsense).
(Other definitions for satyr that I've seen before include "Classical deity" , "Goatlike deity of Greek myth" , "Woodland spirit" , "Goatlike man of mythology" , "Part man, part goat" .)