Second line not going straight through medical service gives you butterflies (8)
I believe the answer is:
monarchs
'butterflies' is the definition.
(I've seen this in another clue)
'second line not going straight through medical service' is the wordplay.
I cannot quite understand how this works, but
'second' could be 'mo' (both are short periods of time) and 'mo' is located in the answer.
'line' could be 'arch' (arch is a kind of line) and 'arch' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'gives you' is the link.
Can you help me to learn more?
(Other definitions for monarchs that I've seen before include "Kings, queens etc." , "Hereditary heads of state" , "Hereditary rulers" , "Kings, queens and emperors" , "Kings and royal rulers" .)