Butterfly active in early spring? (7)
I believe the answer is:
monarch
'butterfly' is the definition.
(I know that monarch is a type of danaid)
'active in early spring?' is the wordplay.
'active' becomes 'on' (I've seen this in other clues).
'in' means one lot of letters goes inside another.
'early spring?' becomes 'March' (first month of spring).
'on' put into 'march' is 'MONARCH'.
(Other definitions for monarch that I've seen before include "Sovereign; butterfly" , "Butterfly - ruler" , "one over realm?" , "Stag in Landseer picture" , "Eg, king, queen, emperor" .)